TUBERCULOSIS

tuberculosis is a disease of man and animals caused by the tubercle bacillus, which belongs to the “ acid-fast ” group of bacteria, some of which are patho- genic and others quite harmless. the most important patho- genic varieties are the “‘ human,” the “‘ bovine ” and the “ avi- an.’’ whether these are to be regarded as distinct organisms or merely as mutations is not yet settled but they are easily dis- tinguished by their selective effects on test animals. tuberculosis, when it has reached the stage at which it is clinically recognisable, may be regarded as the end-result of a slow progressive and long unrecognised bacterial invasion. it should never be forgotten that, in the majority of infected per- sons in civilised communities, this clinically recognisable end- stage is never reached; in other words, only a small proportion of the number of infected persons becomes clinically tuberculous. distribution throughout the world.—a world-survey shows that tuberculosis tends to be wide-spread in densely populated areas linked by commercial and social ties with the outside world, and is rare or absent in sparsely populated and culturally isolated com- munities. climatic, geological and racial factors appear to play a secondary part. density of population, with the opportunities for frequent and close contact with infective persons which jt involves, appears to be all-important in the dissemination of the germ, while wages, occupation, housing, diet, climatic conditions and racial customs constitute ancillary factors of varying significance in so far as they bear upon the capacity of the individual to resist the infective dose or doses to which he has been subjected. 835 with human tuberculosis, it is where men are herded together in the centres of industry that the infection becomes so common as to be almost universal. that this statement is true is proved by the post-mortem findings of reliable pathologists in europe and america who have investigated long series of cadavers of persons dying from all diseases. in the words of m. fishberg “* no matter what the cause of death may have been, whether the persons knew they had tuber- culosis or not, between 50 and 100% of people living in large cities show active, quiescent or healed tuberculous lesions in some organ of their bodies.” these findings bring into sharp relief the importance of the dis- tinction between infection and disease. the results of tuberculin tests applied to healthy persons (pollak, vienna, 1911; mantoux, paris, 1909 and i1gi0; fishbees: new york, 1914; calmette, lille, i911 and others) show that, by the age of 15 years, nearly every individ- ual living under urban conditions has already become infected with the tubercle bacillus. it is clear, therefore, that, in densely populated countries, tuberculous infection is far more widespread than tuberculous disease. in sparsely populated and isolated countries, on the other hand, neither tuberculous infection nor tuberculous disease iscommon. borrel, for instance, found that only 3% of the sene- galese soldiers summoned to europe for the world war gave a positive response to the tuberculin skin-test on arrival in france, while numerous investigations carried out in the african and asiatic colonies and dependencies of the european powers show that primitive tribes living under their natural conditions are almost free from tuberculosis. it has frequently been shown, however, that the members of these primitive communities, on quitting their native surround- ings and coming into contact with the “ tuberculised ” popula- tions of europe, tend to show a marked susceptibility to tuber- culosis; the clinical course, in these cases, being of a rapidly pro- gressive and usually fatal type. it would seem, in fact, that, where there has been little or no previous exposure to infection, the individual remains completel unprotected against tuberculous disease, while, on the other rane there is manifest in the members of communities in which tuberculous infection is wide-spread, a considerable power of resisting the de- velopment of the tubercle bacillus and of rendering latent the active foci of infection. clinical manifestations.—the primary clinical manifestations of tuberculosis tend to vary with the portal of entry of the bacillus. in uninfected subjects, the germs can pass through the mucous membranes of the respiratory and alimentary tracts, without causing, at the moment, any marked local disturbance and their transit thence is easy along lymphatic channels to the nearest lymphatic glands. in these glandular filters, the tubercle bacilli tend to be arrested and there they pullulate and set up the first foci of disease. the formation of secondary foci of infection depends upon the spread of tubercle bacilli from their primary foci in the lymphatic glands to other tissues and organs. the presence of secondary foci thus implies a generalisation of the infection chiefly by way of the blood stream. this generalisation can take place much more easily in susceptible persons than in those who are more resist- ant, and in the young than the old. thus the tendency to widely disseminated tuberculosis is much more marked amongst those groups of individuals in which the “ tuberculin test ”’ shows the highest proportion of negative results. in the infants and young children of european and american communities, the proportion of bone and joint tuberculosis and of tuberculous meningitis is far higher than in adults; while, in the adults of ‘ ae communities, brought for the first time into contact with infection, the same tendency to wide dissemination of lesions is always found. the reactive intolerance implied in a positive response to the tuberculin test which is only acquired as the result of a preceding infection, constitutes a factor of supreme importance in limiting the spread of tubercle bacilli within the body, by causing local inflammation, cell-proliferation and finally fibrosis, with arrest of the wandering germs and their confinement within a fibrous or calcified area. and this reactive intolerance is manifested, not only toward endogenous re-infection from pre-existing foci but to exogenous re-infection from outside the body. pulmonary disease.—with this conception in mind, it is not difh- cult to understand why the tuberculosis of adult life in civilised and 836 “ tuberculised ” communities usually takes the form of pulmonary disease. in the generalisation of infection through the blood stream from the primary lymph-gland foci, the bacillary emboli must travel along the veins from the glands and since all the venous blood must necessarily pass through the capillary bed of the lungs before being re-distributed throughout the body, the lung tissue presents the first filter to be encountered by the blood-borne bacilli. it is into the lungs, too, that all contaminations are drawn in respiration. while both blood-borne and air-borne tubercle bacilli may pass unchecked through the “ virgin’ lung-tissue of children and non-infected adults, they tend, where ‘reactive intolerance” exists, to be arrested in the pulmonary tissue and to set up the inflammatory and ulcerative phenomena of phthisis. i. in great britain changes in clinical type.—the statement is frequently made that the cases of pulmonary tuberculosis encountered 30 or so years ago were much more acute than those seen to-day, and a general impression exists amongst clinicians that phthisis is more acute even now in parts of ireland, scotland and wales than in london and the big industrial centres. this clinical impres- sion receives strong support from the statistical inquiries of j. brownlee (m.r.c. special report series no. 18, 1918), who has shown that, in males especially and to a less extent in females, the age-period of maximum death-rate has steadily receded from the ‘‘ young adult ” group to the “‘ middle age ” group in the suc- ceeding decennia from 1851~60 to the present time. this diminution of the “ young adult ” type of death-rate has, however, been less marked in certain counties of ireland, scotland and wales, and indeed, in agricultural communities everywhere, than in the larger centres of population. brownlee, in the report quoted, suggested that these differences might be due to the existence of para-tubercle bacilli of unequal virulence, but later researches by tulloch have failed to discover any antigenic variants in a large serics of ‘‘ human " tubercle bacilli investigated by him, it may be assumed, therefore, that the recession of the age-period of maximum mortality from early adult to later life implies a more protracted clinical type of pulmonary tuberculosis now than formerly and in the larger centres of population as compared with the more sparsely populated agricultural districts. fall in tuberculosis mortality—as will be seen from the appended table (extracted from the registrar general’s sfatistical review of england and wales for the year 1924, table 6, page 35) there has been, from 1838 onwards, a steady fall in the tuber- culosis death-rate affecting both the pulmonary and all other forms of the disease. this fall, which has been observable in other civilised countries, though often claimed as evidence of the value of modern methods of prevention, was just as marked before the recognition of the infective nature of tuberculosis as after the discoveries of villemin and r. koch had given a definite direction to sanitary effort. clearly therefore, some factor of natural adaptation must have been present to supplement the efforts of preventive medicine. table i. annual mortality at all ages per million persons living i d tuberculosis 7 erculosis of erio (respiratory (all forms) system) 1838-42 (5 years) 4,419 3,782 1847-50 (4 years) 3,714 2,889 1851-5 ‘ : 3,638 2,805 1856-60 ; 3,323 2;572 1861-5 3,313 2,527 1866-70 3,201 2,447 1871-5 2,942 2.017 1876-80 2,817 2,038 1881-5 2,543 1,830 1886-90 2,324 1,635 18gi-5 2,122 1,461 1896-1900 1,906 1/323 1901-5 1,743 r218 1906-10 1,566 1,106 iq = 5 1,404 1,047 1916-20! 1,441 1,107. 1921 1,126 884 1922 1,121 889 1923 : ‘ 1,062 836 | 1924. — 1,058 841 _1the mortality for the years 1915-20 relates to civilians only. tuberculosis the foregoing table is taken from the registrar general's statistical review of england and wales for 1924. those who favour the theory of an ‘ hereditary disposition ”’ to tuberculous infection see in this diminution of mortality the result of the dying off of susceptible stock and the survival of the more re- sistant. others consider that, with the wide dissemination of infec- tion resulting from the agglomeration of large numbers of persons into urban communities, there has been at work a factor of natural auto-immunisation, individuals acquiring various degrees of resist- ance as the result of mild and repeated infections. in favour of the latter theory, it may be said that ‘ acquired im- munity ” plays a part in limiting the spread of other bacterial dis- eases, that even the most susceptible animals may be made relatively resistant to tuberculosis through mild laboratory infections and that a high degree of resistance in any given community, as evidenced by a relatively low death-rate and a relatively chronic clinical type, goes hand in hand with a wide diffusion of infection as proved by tuber- culin tests. prevention.—man is liable to infection from two main sources, the first and infinitely the more important being infected persons and the second, milk from infected cows. not all infected persons are equally infective. those suffering from the chronic type of pulmonary disease with cavities are, perhaps, the most dangerous of all, such cases producing, as a rule, copious expectoration of a sputum heavily charged with bacilli while, being relatively resistant, they often survive for years and are well enough to remain at home. there exist, too, cases whose symptoms are more suggestive of chronic bronchitis or asthma than of tuberculosis and who consequently remain undiagnosed, no precautions being taken. not only the sputum of such persons but the droplets emitted in coughing and talking are sources of danger to others, while the excreted bacilli may accumulate on the clothing and bedding used by them and in the apartments which they occupy. such persons establish the greatest concentration of infective matter within the home, and the smaller, the worse ventilated and the more crowded the home, the more massive the infection and the more serious the danger to others. in the home contact with susceptible persons is most likely—for the home is the nest for infants and young children. it is upon the homes and the families of infected persons that preventive measures must be focussed. | adequate provision of hospital and sanatorium accommodation is also a prime necessity so that infected persons may be removed from amongst their still healthy relatives. the use of sputum flasks, the ventilation of rooms, provision of good food for dependants—all these will help. in france, promising results are being attained on the grancher system by which the young children of tuberculous parents are placed with selected foster parents in country districts. another interesting line of prophylactic effort now under trial in france is the protection of the infants born to tuberculous parents by “vaccination” with living but attenuated tubercle bacilli. a. calmette and c. guerin have succeeded, by special cultural methods, in so reducing the virulence of a selected bacillary strain that it no longer produces tuberculosis but merely a transitory and benign infective process accompanied, however, by the develop- ment, in experimental! animals, of a high degree of resistance against re-infection by virulent strains. this vaccine of calmette (b.c.g.) is now being administered not only to calves but to the infants of tuberculous parents shortly after birth. so favourable have been the results of experiments on laboratory animals that there are real grounds for hope, both as to prevention of human and bovine tuber- culosis. but it will take years to evaluate the success or failure of these experiments. in the interval, the want of any specific prevent- ive measure throws us back upon general measures of hygiene, attempts to diminish the pool of infective persons by improved methods of treatment and the supervision, control and, whcre_ pos- sible, isolation of infected persons through the machinery of the tuberculosis schemes of local authorities and by precautions against the sale or the use of milk containing living tubercle bacilli. general measures of hygiene find their most important applica- tion in arrangements for the conscientious notification of diagnosed -cases, the inspection of “ contacts,” the medical inspection of school children, the provision of ‘‘ clean milk,” the betterment of housing, the adequate disinfection of contaminated articles and places and tactful and efficient ‘‘ health visiting.” recent methods of treatment.—symptomatic treatment, while often affording relief, cannot cure. even “ specific” treatment aiming at the production of immunity, while helpful in certain patients, has proved disappointing. tuberculin, in its various forms, is no longer regarded as “‘ a cure in the strict sense of the tuberculosis term ” and is not entirely free from risk. the natural power of the human body to amplify its powers of resistance is very great and many cases do well if placed under favourable conditions of life. in this lies the secret of “‘ sanatorium treatment ” in which the mode of life of the patient is carefully adjusted to the limits imposed by his disease. within these limits he can exercise and work with benefit to himself and an increase in the amplitude of his resistance. for the more favourable types of pulmonary cases, sanatorium treatment offers a very definite prospect of restoration to average health and working capacity. although so much stress is laid on controlled exercise and work, the basis of the treatment is vest. in the case of ‘‘ surgical tuberculosis,” too, where the bones and joints of the body are affected, we find in rest the greatest of all adjuvants to recovery. a study of the results attained at such english centres as the treloar hospital for cripples at alton, the shropshire orthopaedic hospital, the north wales sanatorium and the metropolitan asylums’ board hospital at carshalton will suffice to prove the curability of sur- gical tuberculosis in children by judicious immobilisation and rest. fresh air (see pubiic heartn), sunlight (see helio- therapeutics) and the artificial sunlight produced by arc lamps are being used, more and more, to help on the results of treatment by surgical rest, and wonderfully favourable results are already claimed for these methods. in pulmonary tuberculosis, too, the method of “‘surgical rest ”’ for the affected part is applicable where the disease is confined or almost confined to one lung; and new vistas are being opened up through the use of artificial pneumothorax apecolysis and thoracoplasty. nothing is more certain than that the surgical treatment of pulmonary tuberculosis is destined to play an in- creasingly beneficient part in the future. but, while all these methods are of proven value in appropriate cases, none of them can be claimed as a cure, and it is to chemotherapy that we turn in our hope for the future. robert koch found that salts of certain metals, and especially gold, had a lethal effect on the tubercle bacillus but only in con- centrations which were also deleterious to the tissues. research however, has continued on these lines, and within the last two years, prof. mellgaard of copenhagen has succeeded in producing a gold compound, sodium aurothiosulphate or sanocrysin, which, while still under test, appears to have a definitely lethal effect on tubercle bacilli in the human or animal body, in concentrations which are non-toxic for the patient. here, again, we appear to be upon the threshold of a great advance in the treatment of tuberculosis. tuberculosis schemes.—up to the end of rgro, the work of fighting tuberculosis in great britain was left, for the most part, to the initia- tive of the more progressive local authorities, supplemented by pri- vate enterprise and the work of voluntary organisations. much knowledge was accumulated through the work of the royal commis- sions of 1890 and 1901 and through the activities of the local gov- ernment board, but there was no co-ordinated national effort to deal with the disease. in nov. 1911, it was made incumbent on every medical practi- tioner attending on or called to visit any person suffering from pul- monary tuberculosis to notify the case immediately to the medical officer of health concerned. these regulations, the outgrowth of orders by the local government board of dec. 1908, were made applicable to all forms of tuberculosis in dec. ig912. in 1911, too, the national insurance act made provision for sanatorium benefit for insured persons, the local government board being empowered to authorise county councils to provide, maintain and manage institutions for the treatment of tuberculosis. under the finance act, 1911, and the insurance act, a sum of £1,500,000 became available for provision of or grants in aid toward sanatoria and other tuberculosis institutions while the govt. under- took to pay 50% of the annual cost of the anti-tuberculosis work carried out by local authorities. the public health (tuberculosis) act of 1921 placed a statutory obligation on each county and county borough council to make arrangements for the treatment of all persons suffering from tuberculosis, whether insured or not. finally, in 1911, a departmental committee, presided over by major (now lord) astor, was appointed to report on the gencral policy in regard to tuberculosis in its preventive, curative and other aspects. the tuberculosis schemes now operative everywhere throughout england, scotland and wales are based, for the most part, on the report of the departmental committee. the units in a complete scheme are as follows:— 837 1. the tuberculosis dispensary or institute -—the functions of this unit are to be “a receiving and clearing-house and a centre for diagnosis, consultation and observation, where persons can avail themsclves of the services of specially qualified medical men.” on the dispensary or institute is based, too, the work of the tuberculosis nurses and visitors ‘‘ who advise and instruct patients in a hygienic mode of life ”’ and help the tuberculosis officer to keep in touch with the homes of tuberculous cases. | 2. residential institutions.—these consist of sanatoria for the more favourable cases and hospitals for those patients unable, at the moment, to benefit by sanatorium treatment. the schemes, in- clude arrangements for home nursing, dental treatment, provision of extra nourishment, training in new occupations and “ after-care.’"! the growth of anti-tuberculosis work in england since the passing of the insurance act may be gathered from the steady increase in expenditure shown in the following table which 1s quoted from dr. coutts’ pamphlet :— table ii]. tuberculosis expenditure (england) payments | from the | exchequer a gross eo 2 in an of . xpenditure rom expenditure } period af local insurance incurred authorities | committees | during the period mentioned | in col. i (1) (2) (3) (4) july 15 1912, to march 31 1913 96,000 34,000 30,000 year ended march 31 iqi4 : ; 373,000 189,000 87,000 year ended march 31 ; 1915 ; : : 595,000 227,000 176,000 year ended march 31 1916 ; ; 700,000 211,000 237,000 year ended march 31 1917 ; , 894,000 251,000 300,000 year ended march 31 igi8 ; , 1,087,000 266,000 384,000 year ended march 31 i9ig ; : 1,285,000 314,000 450,000 year ended march 31 1920 y , 1,954,000 621,000 635,000 year ended march 31 sa sa ig21 ; ; 2,950,000 828,000 i,o11,000 | year ended march 31 1922 5 : 3,074,000 200,000 1,717,000 large as these figures may seem, there is still a vast field to cover if tuberculosis is to be dealt with adequately on the present lines. the actual notifications, amounting for england and wales to 57,737 persons in 1924, or 1-47 per 1,000 of population, are admittedly an under-estimate of the known cases, while the undiagnosed carriers of infection must be more numerous still. if the isolation of infective persons is to become effective—and the public health act, 1925, contains clauses providing for the compulsory hospitalisation of infective cases—it will be neces- sary to face the public maintenance of their dependants while patients remain in residential institutions. and there is an ur- gent need for further expenditure to provide accommodation and treatment for cases of surgical tuberculosis. the best chance of ultimate economy would sem to lie in the endowment of research directed towards effective preventive measures and curative treatment. bibliography.— medical research council, special report no. 18, “epidemiology of phthisis in great britain and ireland,” parts 1 and 2 (1918); special report no. 33, ‘“* pulmonary tuberculosis; mortality after sanatorium treatment ” (1919); special repori no. 46, “ epidemiology of phthisis in great britain and ireland,” part 3, stationery office, london (1920); special report no. 67, “report on artificial pneumothorax,” stationery office, london (1922); see also sir a. newsholme, the prevention of tuberculosis, and ed. (1910); sir j. k. fowler, pulmonary tuberculosis (1921); c. riviere, the early diagnosts of tubercle, 3rd ed. (oxford 1921); thid., problems in tuberculosis: administration, diagnosis, employ- ment, settlements (oxford, 1923). (s; ls gc, 1 for a full account of this subject a pamphlet on ‘f anti-tubercu- losis measures in england,”’ by dr. f. j. h. coutts, c.b., senior medical officer, ministry of health, may be consulted. 838 il. in the united states a more or less continuous decline in mortality from tu- berculosis had been noticeable in the united states since about 1880; but between 1910 and 1924, and especially after 1917, the decline was extraordinary. the death-rate for the disease fell from 202 per 100,000 population in 1900 to 160 in i9io; 150 1n 1917; oi in 1924; a reduction of 55° for approxi- mately the first quarter of the century, and of 21% for the first decade, only 6% from 1910 to 1917, and 39°% between 1917 and 1924. although the statistics have not yet been compiled it is estimated that the tuberculosis mortality for 1925 will show a further decline, to about 88 per 100,000. such a diminution of mortality in a disease like tuberculosis is unparalleled in the annals of epidemiology. in rors tuberculosis, which had always been the first cause of death, yielded its unenviable pre-eminence to heart disease. it has since been outranked also by pneumonia, cerebral haemorrhage (apoplexy), and cancer, so that in 1924 it occupied fifth place or near the foot of the list of major diseases. as usual, pulmonary tuberculosis accounted for about seven- eighths of all deaths due to the disease. urban communities—all sections of the country and all ele- ments of its population participated in the great betterment. but urban communities, as exemplified in new york city, out- stripped the rural districts in the control of the disease. in them tuberculosis is declining more rapidly than in the country at large. in rg900 new york city’s tuberculosis death-rate was 280, or 39% higher than that for the nation; by 1920 it had fallen to 126, or only 11% greater; and in 1924 it was 93, or barely 2°% in excess of the general rate. such changes are revolutionary and, for a great and crowded city, are unparalleled in the history of tuberculosis. they may be better appreciated by reference to the accompanying chart, which suggests that in 1924 2 new york citizen’s chance of dying of tuberculosis was less than one-half that in rg1o and one-third that in r900. among infants and children the reduction of tuberculosis has been almost sensational. in new york city the death-rate for infants in 1923 was only one-sixth that of 1898 (94 in 1923 and 609 in 1898), while for children under 15 the decline between the two years was from 136 to 33. causes of decline —much has been written about the causes of the continued, and of late the extraordinary, decline of the disease. the phenomenon is apparent in all countries under our industrial type of civilisation, although latterly it has been most marked in the united states. the presumption is therefore strong that broad economic and social movements which char- acterise our era, though they elude close definition, are potent factors. undoubtedly, the amelioration of existence, a resultant of the enormous increase of wealth in the united states, has played its part. but two other instruments have also been brought to such effectiveness inthat country as to be likewise decisive in the control of tuberculosis. organisation of control.—the first is the national tuberculosis assn., founded in 1904. through its central office in new york city and its hundred and more subsidiary state and civic bodies, this organisation extends its influence into every hamlet, as it maintains services and agencies to be applied to every phase of the disease. its funds are recruited through the unique manner of selling, every year at christmas-time, its so-called “‘ christmas seals ’’ stamps to be affixed to postal matter but not for postage. their sale has become so enormous as to bring an annual gross return of almost $5,000,000 though they cost but a cent each. sanatoria.—as organisation js the key-note of the social control of the disease, so ts the sanatorium the keynote of its medical control. in no other country has the sanatorium movement been so highly developed. twenty years ago, when death-rates were around 200, there were hardlv a score of these institutions in the united states. in 1925 they numbered more than 600, with a capacity of 52,460 beds for civilian patients and 13,940 beds for federal patients, veterans of the wars. their annual’ “ turn- over ’’ was approximately 150,000 patients, or perhaps one-fifth of those ill with the disease. the standard of institutional facil- ities has been put at one bed for every annual death. on this tukhachevsky basis the united states, with 78,096 deaths from pulmonary tuberculosis in 1924 (registration area), has perhaps two-thirds the ideal equipment, omitting the beds for federal patients. special treatment.—of special methods of treatment, artificial pneumothorax (g.v.) has become a standard procedure, much employed in selected pulmonary cases. since 1920, more radical surgical measures, such as the various forms of thoracoplasty, have been on trial; their use is increasing rapidly. heliotherapy (q.v.), sun treatment and other forms of light therapy are now in common use in non-pulmonary disease. specific treatment (tuberculin) valuable only in expert hands, holds its own. chemotherapy has made no headway; nor have the various preparations, advocated recently on the continent of europe (senocrysin, krysolgan, etc.) been, as yet, received kindly in the united states. of all diagnostic measures, the x-ray (g.v.) has had by far the greatest development, and has become in- dispensable. it has not, of course, superseded physical exam- ination; and it is noteworthy that time brings a growing ap- preciation, that diagnostic precision and refinement are to be attained only through the co-operation of the examining physi- cian and the rentgenologist. no specific or laboratory test has been found decisive in diagnosis, except the long-recognised demonstration of tubercle bacilli in tissue products. immunity.—the practitioner of 1925 regarded tuberculosis from a point of view quite different from that of tg10. the disclosure that tuberculosis exists as a latent infection in almost all people, and that infection confers a measure of specific im- munity to reinfection, gave rise to the almost necessary pre- sumption that adult pulmonary tuberculosis develops from in- fection acquired in childhood and that the adult is insusceptible to exposure to infection from without. but latterly an increasing number of studies of american authorities has brought about some modification of too rigid an adherence to this opinion. they have shown that conditions are only relative. although early infection and a resulting immunity are conceded, it is pointed out that infection is capable of complete healing, with a consequent great diminution or even disappearance of immunity; and that, therefore, there is every likelihood that reinfections— and active disease from them—are possible at almost any period of life. in 1915 there occurred the death of edward l. trudeau, the recognised pioneer and leader of tuberculosis activities in the united states. in the next year was held the first session of the trudeau school of tuberculosis, the first of its kind, in saranac lake, n.y., to give systematic instruction to physicians. in 1917 was issued the american review of tuberculosts, a monthly scientific periodical, founded by the national tuberculosis association. it was in 1925 the only tuberculosis journal in the united states, and had done much to stimulate the study and investigation of the subject. among the more prominent centres of research in tuberculosis were the trudeau foundation at saranac lake, the henry phipps institute at philadelphia, the kenneth dows laboratories of johns hopkins university at baltimore, the national jewish hospital for consumptives at denver, the municipal sanitarium in chicago and the colorado foundation at colorado springs, all of which were established since ig10. (a. k. k.)} tukhachevsky, mikhail (1893- }, russian soldier, was born in the government cf smolensk. he received the best russian military education in the corps of cadets and the alek- sandrovsky military school, out of which he passed in july 1914. in feb. 1915 he was taken prisoner by the germans, and, after several fruitless attempts to escape, he succeeded in the autumn of 1917 and made his way back to russia. he was at once taken into the military service of the soviet, took part in the operations in defence of petrograd (leningrad), and in june 1918 re- ceived the command of an army. he commanded successively the i., viii. and v. armies and then the caucasian front. after the successful conclusion of operations against denikin, tuk- hachevsky was given the command of the western front. after the civil war he became chief of the military academy, and in april 1924 was appointed assistant chief-of-staff. tulsa—turbine, steam tulsa, okla., u.s.a. (see 27.368), in the midst of the rich, oil-producing area of northeastern oklahoma, increased fourfold in population in the ro years after rg10, reaching 72,075 1n 1920 (109-3 males to roo females), of whom 8,878 were negroes and only 2,025 foreign-born. in 1925 the census bureau estimate was 124,478. annexations of land brought the area to 12 sq. m. in 1925. in 1925 there were 1,500 individual firms engaged in the oil business. the international petroleum exposition was estab- lished in 1923, on its permanent ground of ro acres. manufac- tures developed rapidly, until in 1923 there were 106 establish- ments producing goods valued at $22,327,907. debits to in- dividual accounts in tulsa banks amounted to $1,181,952,000 in 1923. civic improvements, up to 1925, included the adoption of a town plan, a regional plan and zoning regulations; the extension of the park system until there were 13 larger parks, con- taining 2,385 ac., and numerous small playgrounds; and the completion of a water-supply system at a cost of $8,000,000 which brings soft ozark mountain water from a reservoir of 20 billion gal. capacity in the spavinaw hills, 60 m. distant, over and under rivers, hills and ravines, by force of gravity alone, although the difference in the elevation of the source and the terminus is only go feet. in june 1921 there was a serious race riot, in which more than 25 persons lost their lives and many more were injured. as a consequence, the county was placed! under martial law by the governor for a time in 1923. the old council tree of the creeks, a huge spreading elm, still stood (1926) in the grounds of a private residence. tunisia (sce 27.393), area about 50,000 sq. m.; population (1921) 2,093,939. the natives numbered 1,937,824, of whom 48,436 were jews. the europeans numbered 156,115 and in- cluded 54,476 french, 84,799 italians and 13,520 maltese. tunis, the capital, had 171,672 inhabitants, sfax 109,754 and bizerta 20,763. , history.—the protectorate form of government was main- tained, the bey being the head of the regency, while the french resident-general controlled the administration, the army of occupation being 25,000 strong. mohammed en nasr, who had been bey since 1906, died in 1922, and was succeeded by his cousin mohammed el habib (born 1858). during the world war tribesmen from fezzara, led by turkish officers, attacked the french outposts in southern tunisia. there was some sharp fighting in sept. and oct. 1915, when the french re- established order. later on large numbers of tunisian soldiers were employed in france. in 1919~—20 by agreement with italy the territory on the sahara south of tunisia forming salients be- tween the oases of ghadames and ghat and between ghat and tummo was transferred by france to tripolitania. as the census figures given show, the majority of the european inhabitants are italians or maltese. as part of an effort to give the protectorate a more french character, decrees were issued in 1921 declaring that british (¢.e., maltese) and italian subjects, born of parents who were themselves born in tunisia, would be deemed to be of french nationality. these decrees provoked resentment, especially among the italians, whose right to maintain their nationality was protected by a convention of 1896 still provisionally in force, and no settlement of the question with italy had been reached by 1926. as to the british, an arrangement was reached with france in 1923 whereby the persons afiected were entitled to decline french nationality. in 1922, in order to give tunisians a larger share in the ad- ministration, a general council for the protectorate, consisting of 44 french and 18 nominated native representatives, and also regional councils, were established. the general council super- seded the consulting conference set up in 1905, and had greater powers than that body. there had already arisen a nationalist agitation, and this in 1924~5, when the cost of living was four times as great as in 1914, was mixed up with a communist agita- tion accompanied by some disturbances in the towns. the communist agitation was not deep rooted, but among educated tunisians there was a demand for a democratic form of govern- ment. this demand was not met, but as an educational measure 839 further powers were conferred in 1925 on municipal councils. in archaeology important excavations were carried out at carthage and other sites, and efforts were made to attract tourists. industry and trade.—tunisia is essentially an agricultural country, but has also very valuable mineral resources. the average annual export of wheat in the period 1915-24 was 319,000 quintals, of barley 627,000 quintals. tunisian olive oil is of very high quality; there were in 1924 8,000,000 fruit-bearing olive trees, and the production of oil was 220,000 quintals. tunisian wines, mostly red, are of some repute, and some 600,000 to 800,- ooo hectolitres are produced yearly. of minerals the production of phosphates was 1,882,000 tons in 1912, had fallen to 819,000 tons in 1918, and had risen to 2,400,000 tons in 1924. iron, lead, zinc and manganese ores are also exported in considerable quanti- ties. marine salt of a superior quality is produced to the extent of some 300,000 tons annually— it is exported to places as far apart as india and the united states. in 1913 imports were valued at 144,000,000 fr. and exports at 185,000,000 fr.; for 1924 the figures were imports 927,940,000 fr., exports 582,350,000 francs. the tunisian franc follows faithfully the movements of french currency, so that no exact comparison can be drawn between the figures of 1917 and 1924. more satisfactory evidence of prosperity was found in the in- creased production, while the excess of imports was due to the comparatively rapid development of the country’s resources— only a small part of the imports were for articles of luxury. external trade was increasingly with france, the combined result of a protective tariff and the low exchange value and instability of the franc. next to france trade is chiefly with italy, great britain and the united states. the british trade was in 1924 some 17 % of the total. considerable sums were spent, from the raising of loans, on railways, agriculture and colonisation by french settlers. the budget figures of 1924, for ordinary receipts and expenditure, showed a surplus of 40,413 fr. on a total revenue of 219,130,800 francs. in rors (with the franc at par) revenue had been 60,000, - ooo fr. and the surplus 1,470,000 francs. birliography.— statistique generale annuelle de la tunisie (paris); reports on the trade of tunisia (dept. of overseas trade, london); de lanessan, la tuntsie (paris, 1917); j. saurin, le peuplemeni francais en tunisie (paris, 1918); l. e. douglas, behind tunistan waits (london, 1923); a. bernard, enguete sur l’habitation rurale des indigenes de la tunisie (tunis, 1924); e. fallot, ‘‘ la delimitation entre les territoires francais et italiens du sahara,” f’afrigue fran- caise, vol. 34 (paris, 1924). {(f. r. c.) tupper, sir charles (1821-1915), canadian statesman (see 27.410), died oct. 30 1915. turbine, steam (see 25.823 and 842, also steeam engine). the reaction and impulse principles—since the kinetic energy in a jet of steam issuing from a nozzle resides entirely in the velocity of the steam, it follows that to utilise the energy efficiently the steam must be brought as nearly as possible to rest. there are two methods by which this can be accomplished. either the nozzle itself may be caused to move backwards with such a velocity that the issuing jet of steam remains stationary in space or on the other hand the jet of steam may be made to impinge on a moving blade system and its velocity thus abstracted. the words “reaction”? and “impulse” are used respectively to designate the two principles outlined, and the same terms have now come into general use as descriptive of turbines which embody, more or less, the respective principles. the development of the steam turbine as a practical machine dates from 1884 when sir charles parsons patented a design in which the total range of steam pressure which it was desired to utilise was divided up into a large number of stages, the small velocity energy due to each partial drop of pressure being ab- sorbed before the next partial drop occurred. the complete turbine thus consisted of a number of elementary turbines work- ing in series, each of which, having only a small steam velocity to deal with, could operate efficiently with quite a low blade speed. the parsons principle of “ pressure compounding ” a {urbine in this manner can be taken advantage of in two ways. if each partial pressure drop takes place in a set of fixed nozzles, 840 so that steam at the full velocity due to this drop impinges on the running blades, we have what is known as the pressure com- pounded “ impulse ” turbine. if, on the other hand, the steam is arranged to expand in both the fixed and running elements of the turbine, so that the mov ing blades are impelled chiefly by the reaction of the steam issuing from them, the machine is called a pressure compounded “ reaction ” turbine. . various types of turbine the parsons.—the inherently high efficiency of the reaction water turbine was well known to engineers prior to 1883, ard for this reason the original compound steam turbine of sir charles parsons was constructed as a “ reaction ” machine. the reaction principle as developed by him at ifeaton works, new- castle-on-tyne, has since been embodied in turbines aggregating millions of horsepower and is the principle employed in many of the largest and most efficient plants in the world. the first parsons turbine was constructed in 1884-5. it consisted of a rotor about 3 in.in diameter carrying numerous rings of outwardly projecting brass blades which alternated with corresponding rings of fixed blades projecting inwards from the casing. steam was admitted at the centre of the casing and flowed axially to the exhaust at each end. the partial expansion of the steam in each row of the fixed blading generated a velocity which was absorbed by the succeeding row of moving blades, while the similar partial expansion of the steam in the latter tended to urge them forward by its reactive effect. the action of the steam was identical with that employed in the reaction turbine as built to-day. this early machine was directly coupled to a 4 kw. parsons dynamo which it drove at a speed of 18,000 revolutions per minute. it used steam at a pressure of 60 ib. per sq. in., and exhausted to atmos- phere, its steam consumption under such conditions being about 200 lb. per kw. hour. it worked satisfactorily for several years, and, owing to its historic value as the prototype of the modern steam turbine, has since been placed in the south kensington museum (see fig. . on plate). the de laval.—in the year 1887 de caval patented an im- proved impulse turbine, the essential feature of which was the employment of a diverging nozzle to develop the velocity due to the full pressure drop of the steam and to direct the latter on to the blades of a sirgle wheel. the invention of the diverging noz- zle was a highly important one in connection with impulse tur- bines, as without it only a small range of expansion could be efficiently utilised. since in the de laval turbine the whole of the energy of the steam was to be absorbed in a single stage, very high blade speeds were necessary, and these implied very high speeds of rotation. the wheel was of special design to withstand the severe centrifugal stresses involved and it was mounted on a very thin flexible shaft in order that it might be able to rotate about its own centre of gravity and principal axis when running. the wheel of a 5 h.p. turbine had a diameter to the centre of the blades of only 3-94 in., and ran at no less than 30,000 revolutions per minute. in a machine of 300 h.p. the wheel was 29:92 in. in diameter and made 10,600 r.p.m., giving a mean blade speed of 1,380 ft. per second. at such speeds of revolution direct driving was impossible, so de laval incorporated double-helical gear in the design, giving a speed reduction ratio of about ten to one. owing to greater limitations to permissible stresses in larger disks and to the difficulty of providing sufficient nozzle arca round the wheel, turbines of this type have not been constructed in sizes developing more than a few hundred h.p., but within their limitations they are moderately efficient machines. by the invention of the diverging nozzle and high-speed mechanical gearing, de laval made two important contributions to turbine development. the compound impulse-—the typical impulse turbine of to-day owes its development principally to prof. a. rateau of paris, whose work on steam turbines dates from 1894, when he first devoted his attention to simple impulse machines of the de laval type. the essential feature of the modern rateau 1 throughout this article the value of one kilowatt is understood to equal 1-34 horsepower. turbine, steam turbine is the use of a succession of simple de laval impulse wheels in series in the steam flow, 7.e., compounded on the parsons principle of subdivided pressure drop, already described. all subsequent designers of successful impulse turbines have followed ithe lines laid down by rateau, except as regards certain minor details of construction. modern machines of the compound impulse type have been constructed in sizes up to 60,000 kw. capacity, and high efficiencies have been obtained. a feature that is peculiar to impulse turbines is the ease with which the admission of steam may be restricted to a part only of the circumference of the bladed wheels, by admitting steam through nozzle groups subtending only a small arc. it is now recognised that this results in a certain loss of efficiency due to the fan-action of the unoccupied blades, but on the other hand it permits the substantial advantage of using blades of a rea- sonably large height running at an adequate velocity at the high pressure end of the turbine, where the volume of steam to be passed through the nozzles and blading is but small. an- other special feature of the impulse turbine is that, since the steam can be expanded in the nozzles to a moderate pressure before entering the body of the machine, no part of the main casing or of the wheels or blading system need be exposed to steam at the initial high pressure or temperature. the losses due to disk friction of the wheels running at high speeds in a com- paratively dense medium, and those due to the comparatively high velocity of the steam through the blades, are however con- siderable. the curtis——the essential feature of the curtis turbine was the combination of the expanding nozzle of de laval with “ ve- locity compounded ” blading. the steam entered the blading of each stage at a comparatively high velocity, acting on a wheel carrying two or more rows of blades, alternating with fixed blades projecting from the casing. after acting on the first row of moving blades it was deflected back on to the second row by the fixed, or “‘ guide ” blades and so on, its velocity being con- tinuously reduced. as many as four moving rows per wheel were adopted in some instances, and thus a high initial steam velocity could be dealt with by blading running at a very moderate speed. it is, however, very dificult to obtain a satisfactory efficiency with several rows of impulse blades working in series in this fashion, and the use of two rows only per pressure stage became general. reaction machine in which the alternate rows of blading are arranged to project axially from opposed discs which rotate in opposite directions. each disc is mounted on the end of a separate shaft carrying an alternate rotor, the two alternators working electrically in parallel and each contributing half the total output of the machine. the steam is introduced between the centres of the bladed discs and flows radially outwards, escaping at their circumference to a space connected with the condenser. since both blade systems rotate, the relative blade speed is double that which would correspond to the speed of rotation at which each of the alternators is driven, consequently the required degree of pressure compounding can be obtained with a reduced number of blade rings. the similarity of the discs and the method by which the blade rings are fixed, morcover, practically eliminate difficulties due to distortion when running, and very fine clearances can therefore be used. combined types.—the velocity compounded wheel of curtis is frequently used for the first pressure stage of a turbine of which the succeeding stages are either of the reaction or of the simple impulse type. the builders of compound impulse machines frequently seek higher efficiency by arranging for a certain amount of expansion of the steam in passing through the blading, thus partially adopting the reaction principle. the construction of turbines consisting of a multi-stage pressure-compounded high-pressure cylinder, followed by a low-pressure cylinder of the reaction type has been advocated and several such machines have been built. the idea of constructing a turbine in more than one cylinder is not new, having been first adopted by parsons in the 2,000 s.h.p. turbine engines of the stcam yacht. steam turbines plate beng / valve d yacuum <i” va birect : ' guptanl & c “ oynramo § - faciter | a - tad | . john gene ss | gee | n* | - iad ae ~ | ¥) ; eo | wie me le a alternating current | ez, 1 , } electric generator | = a =¥y | twin vertical | “i | a . 2 condensers 7 »_ conical passage -way te ‘ ’ iis > koay l.p . alternator l.p turbine ~ /.p turbine fic. 1. the first type of parsons machine (science museum, london). fic. 2. 10,000 k.w., 3,000 r.p.m. parsons reaction steam turbo alternator, fig, 3, 50,000 k.w’. parsons reaction steam turbo alternator, arranged cross compound on 3 shafts (i.p. and l.p. in line), speeds, h.p. and i.p. 1,800 r.p.m. l.p. 720 r.p.m. turbine, steam * turbinia ” in 1879 and in the 1,000 kw. turbines constructed for elberfeld so long ago as 1900. in the combined type referred to, the impulse portion contains an unusually large number of wheels, which are of comparatively small diameter and turned from a solid forging. the blade speeds and steam speeds are theretcre low and the disk friction is also less than would be the case with larger wheels. present position of the turbine so rapid has been the development of steam turbines since the construction of the first turbine of ro h.p. in 1884 that their position as prime movers for the generation of electrical energy and many other purposes is now unrivalled. the successful de- velopment by parsons of double-helical gearing for the trans- mission of large powers has permitted complete freedom of choice with regard to turbine speeds, so that the steam turbine, which is essentially a high-speed prime mover, can be employed with advantage for driving machinery which is required to run at any moderate or even low speed. mechanical gearing has, for example, supplied the solution to the problem of the continuous current turbo-dynamo. moderate speed generators have now reached an output of 3,000 kw. from a single machine, the current collected from a single commutator being as much as 6,000 amp., and with the interposition of gearing such generators can now be turbine-driven. turbines of only a few horsepower are now frequently used to drive fans, centrifugal pumps and auxiliary apparatus used in connection with power stations, and there appears to be almost no limit to the applicability of the turbine as a prime mover. for steam railway locomotives, the reciprocating engine still holds its own, but there are signs that the turbine may also find a place. progress in this direction has been hindered by the two practical difficulties of reversing the locomotive easily, and of constructing a satisfactory portable condenser. the variable speeds at which locomotives must run also impose a condition adverse to the turbine. nevertheless the construction of the reid-ramsay locomotive in great britain, and particularly of the ljungstr6m locomotive in sweden, the latter operating in regular service with a fuel consumption only half that of recip? rocating-engine locomotives on similar duty, indicates a possible development in this direction (see ratlway engineering; locomotive design). trend of modern design.—the broad difference in the prac- tices of to-day lies between the so-called impulse and reaction principles as applied to horizontal compound turbines. the arguments in favour of either type may be based either on pref- erence for the mechanical construction appropriate to it, or on the theoretical efficiency to be obtained from it. the cost of manufacture is also an important commercial factor. this last consideration tends to the construction of impulse turbines with comparatively few stages, seven or eight being commonly employed in a medium-size machine. such machines are short and compact, but the high steam velocities inherent in the de- sign involve serious frictional and eddy losses both in the nozzles and blades. trouble with erosion of the blades, especially towards the low-pressure end of the turbine where the steam is wet, is also sometimes experienced. the much lower steam velocities, due to the many times more numerous stages which are usual in a reaction turbine are favourable to efficiency. moreover, since the steam velocities in a pair of fixed and moving blade rows in a reaction turbine are identical, considerations of symmetry would indicate that a higher efficiency would be ob- tainable than in a turbine in which the whole of the expansion per stage took place in one clement (the nozzles). it is interesting to note that builders of reaction machines have experimented with different ratios of expansion in the fixed and moving elements, but up to the present the practice of using equal ratios has proved to be the best. an approach towards the reaction principle has been advocated by some builders of impulse turbines, who con- sider it better to allow a certain amount of expansion to take place in the moving blades, but opinion is by no means unani- mous on this point. sat in modern practice the best results as regards blade efficiency are obtained with a ratio of blade speed to steam speed of about o-85-0-90 in the case of reaction turbines, and o-43-0-48 in the case of impulse turbines having a single row of rotating blades after each set of nozzles. the diminution of nozzle efliciency with increasing velocity of the steam has been con- firmed by recent investigations of the steam nozzles research committce? but there yet remains to be found the exact cause of this loss of efficiency and whether its reduction or elimination is possible. another point which bears upon steam turbine design is the experimental fact that the stage efficiency of a turbine is less with saturated or wet steam than when the steam is superheated. phermodynamics of turbine designu.—these problems are closely associated with the thermodynamics of turbine design. all engineers engaged in such work are desirous of making the design of nozzles and blading a matter of exact calculation, and are also anxious to be able to agree upon a rational basis of com- parison for the performances of different turbines working with different steam conditions. up to the present these problems are not completely solved, the influence of the cumulative heat due to the inefficiency of the several stages of a turbine, and the experimental fact of decreased stage efficiency where wet steam is found, having made exact calculation somewhat difficult. the proportion of the heat supplied to the steam in the boiler that is converted into useful work, does not depend upon the efficiency of the turbine only, but is a function of the conditions under which the heat is received and rejected. the efficiency of the thermodynamic cycle, which governs the relation between the available energy and the heat supplied to the steam, is ex- plained in the article on thermodynamics (q.v.). attention has been turned to the possibilities of increasing the available energy itself by extension of the thermodynamic cycle, more particularly in the case of land turbines which operate under much less restrained conditions than those prevailing at sea. by the use of higher pressures and temperatures (see steam engine), the lowest possible vacuum and other devices, it is not unreasonable to expect to reach an overall thermal efliciency (from fuel to electricity) of 30% or in other words an efliciency not inferior to the best attained by oil engines, even neglecting the oil consumed in cylinder lubrication. with regard to the possibility of increasing the thermodynamic efliciency by extending the lower end of the temperature range, which the turbine can utilise to an extent completely beyond the range of the reciprocating engine, a limit is imposed in this direc- tion by the temperature of the cooling water available. a con- denser temperature of about 70° f., corresponding to an absolute pressure of 0-36 lb. per sq. in., or a vacuum of 29:25 in. of mer- cury (barometer 30-00")is about as low as can be maintained in practice under favourable conditions. the effective use of such a vacuum demands, however, the provision of adequate blade arca and passage way for the low-pressure steam, which is of great volume. throughout the stages of a turbine the criterion of efficiency is the ratio between the blade speed and the steam speed, and the areas of the blade passages must successively increase in such a manner as to maintain the desired velocity ratio. the axial component of the steam velocity is carried on from stage to stage without appreciable loss. it is even built up to higher values as the peripheral and steam velocities increase. its final loss at the exhaust end of the turbine, however, is prac- tically unavoidable, and with the high peripheral speeds adopted in most low-pressure blading at the present day, an exhaust blade area which gives a perfectly satisfactory velocity ratio may entail a loss of energy in the issuing steam of considerable amount. such loss 1s augmented if, for the sake of weight or cost, any sacrifice is made of the final velocity ratios, which sacrifice might otherwise be a perfectly justifiable compromise. it is evident, therefore, that the exhaust end of the turbine requires separate treatment in its design from the point of view of limitation of the ‘see proceedings of the institution of mechanical engineers, jan. 1923 ef seq. 842 leaving loss, that is, the energy lost in the issuing steam. broadly speaking, where high efficiency is the aim, this consideration imposes a limit upon the axial velocity of the steam in the final annulus. for a given vacuum, therefore, the area of the final annulus must increase in proportion to the output, and for a given output any increase in the vacuum involves an increase in the area of the final annulus. it will be seen, therefore, that any effort to extend the steam cycle, by lowering the temperature of condensation, brings at once into prominence the problem of the exhaust end. | various expedients have been adopted for the purpose of sur- mounting this limitation. the area of the final annulus can be increased by increasing the blade height, and any means of extending the height permissible on a given diameter is valuable for this purpose. thus in many turbines, the blades of the last stages are made of varying section and discharge angle, per- mitting a greater length ratio without unduly increasing the centrifugal stress. another method, commonly employed in both land and marine turbines, is to carry out the final stages of the expansion by divided flow, as for example in a double ended low-pressure turbine, the steam entcring at the middle and flowing in each direction towards an exhaust at each end. in such an arrangement two exhaust pipes are provided and fre- quently two condensers. in another example of divided flow, some makers double only the last row or last few rows of blading, employing specially shaped passages to conduct the steam to the divided portion from the preceding stages. the design of exhaust end advocated by baumann is yet another attempt to overcome the same difficulty. in this device instead of carrying over a part of the steam by special ports to additional blade rings, it is made to flow through inner annuli of the preceding blade rings, the vanes of these inner annuli being specially shaped to reduce the resistance involved to a minimum. if no restrictions are imposed, either upon the diameter of the exhaust end or upon the speed of revolution, a simple and prob- ably the best solution of the exhaust area problem in large machines is to provide a separate low-speed turbine of large diameter for the final stages of the expansion, having blades of normal profile throughout, and correspondingly high efficiency. this low-speed turbine can be arranged in close proximity to the condenser, so as to reduce to a minimum both the length and the resistance of the exhaust passages. in the exhaust passage itself, it is not sufficient to provide area to reduce the mean velocity of the steam passing through it to a moderate value, but the exhaust steam must be distributed into the passages uniformly, so that the velocity is everywhere nearly the same. neglect of this requirement lcads to unneces- sary hydraulic losses, and may also cause troublesome blade vibration in the final stages. many attempts have been made to obtain the benefit of the diffuser principle, which has been so commonly adopted in the case of water turbines, but in the case of steam turbines without substantial success. in any attempt to carry this principle into effect, ample exhaust pipe area should be provided, with pro- gressively larger cross section on the way to the condenser, so that the exhaust steam from the last row of revolving blades is gradually slowed down, with a possible recovery of static head. the practical difficulties in the way of such recovery of pressure in the exhaust steam are very great, and the best that can be done in this direction would appear to be to utilise the leaving velocity of the exhaust steam to overcome the resistance to flow in the exhaust passages, so that the absolute pressure at entry to the condenser is the same as at the exit from the blading. modern practice with regard to these matters may, perhaps, be best exemplified by the large parsons turbine plant (see hig. 3 on plate) erected (1925) in the new crawford avenue power sta- tion at chicago, where, after allowing about 3% for the total power absorbed by the auxiliaries, an overall thermal efficiency (from fuel to electricity) of 27-80% is anticipated.! developments in marine turbines.—the design of the earlier marine turbine installations was largely a matter of compromise 1 for a full account of this plant see engineering, vol. 121, p. 283. turbine, steam between the high speed of revolution desired for the turbine and the much lower speed which was more suitable for the propeller. like all compromises, each side had to sacrifice something and although a satisfactory efficiency could be obtained in the case of high-speed vessels, it was realised that a much greater economy would be possible if both turbine and propeller could be arranged to run each at its own most eflicient speed of rotation. this was of course impossible so long as both were directly coupled to- gether. by the introduction of gearing between the turbine and the propeller, the desired freedom of each with regard to speed was obtained, and thus the turbine not only became applicable to slow-speed vessels, but better results were obtainable even in high-speed vessels, such as warships, liners and channel boats where the direct coupled drive was already firmly established. a small example of marine turbine reduction gearing had actually been built in 1897, in connection with a twin-screw jaunch in which the parsons marine steam turbine co. fitted aio h.p. turbine driving the two shafts by means of helical gear- ing with a speed ratio of 14:1. in 1909 the “ vespasian,”’ a cargo vessel of 4,350 tons displacement, was fitted with geared turbines driving a single propeller. the vessel had previously been equipped with triple expansion reciprocating engines of the usual type and before these were removed they were put into perfect order and very careful tests were made to determine their efficiency and performance. the geared turbines drove the same shaft and propeller as the engines had done and were supplied with steam from the same boilers. the power developed was about 1,000 h.p. and the shaft ran at 70 revs., the gear ratio being 19°9:1i in a single reduction. the installation of the turbines resulted in an increase of about one knot in speed for the same coal consumption, or alternatively a saving of 16% in fuel con- sumption, and the results of the trials were convincing as to the advantages of geared turbines over reciprocating engines. after the ‘ vespasian ”’ had run 18,coo m. in regular service, the pinion was examined and found to be in perfect condition, the wear not exceeding 0-002 inches. (see truns. i.n.a., 1910 and iqii.) | the success of the ‘ vespasian ” led to rapid developments. in rgto the british admiralty introduced mechanical gearing, the torpedo boats “‘ badger”? and ‘ beaver ”’ being the first warships to be fitted with geared turbines. in these vessels each l.p. turbine drove its shaft directly but the h.p. and cruising turbines were geared to a forward extension of the l.p. turbine rotor. at full load about 3,000 h.p. were transmitted through each set of gearing. six years later complete gear drives had become the standard practice for british war vessels of all types and by 1920 some 6s0 gears, transmitting an aggregate of 7,280,000 h.p., were fitted or on order for the royal navy (tos- tevin, trans. 1.n.a., 1920). numerous tests have been carried out to determine the mechanical efficiency of large marine turbine reduction gears. the efliciency of a single reduction gear at full load should be over 98%, and efliciencies of 98-5% have been recorded. with double reduction gear the efficiency is over 97%. these figures include bearing friction. no method of obtaining speed reduction by hydraulic or electrical methods has yet been devised which has approached the efficiency obtainable with mechanical gearing. since the introduction of mechanical gearing the marine turbine has tended to become assimilated in type to the land turbine, the same conditions making for thermal efficiency, namely, high velocity ratios, high steam pressures and tem- peratures and high vacua, being equally applicable. an arrange- ment of turbines in which the high pressure portion of the expansion is confined to a small high-speed turbine, is advanta- geous for the improved thermodynamic systems already referred to in connection with land practice, and such systems with high boiler pressure and temperature are now on the point of being introduced into marine work. assuming such a design to be adopted for an installation of about 5,000 s.h.p. with boiler pressure 500 lb., maximum temperature yoo° f., feed heating to 350° f., and effective air pre-heating to give a boiler efficiency of about 84%, a careful estimate based turin —turkestan on known performance shows that, owing to the increased avail- able energy of the steam and when burning oil, a fuel consump- tion of about 0-55 lb. per s.h.p. would be obtained for turbines only and about 0-65 1b. per s.h.p. for all purposes including auxil- lary machinery. an installation on such lines is now under construction for a clyde steamer which will therefore be the pioneer of this im- proved method of propulsion. the machinery will have a propulsive s.h.p. of 3,500 on two shafts with a boiler pressure of 550 lb. per sq. in. and a temperature of 750° fahrenheit. ‘the principle of stage feed heating is to be adopted. the feedwater will first be heated to about 200° f. by the auxiliary exhaust steam and then raised to a higher temperature in a second heater by steam withdrawn from the turbines. the boilers will be coal- fired and the air to the furnaces heated by the flue gases by means of air preheaters arranged in the uptakes. it is antici- pated that this installation will satisfactorily demonstrate the practicality of applying the latest land practice to marine work and will pave the way to a considerable advance in economy in marine propulsion. two examples of such applications, for total outputs of 27,000 and 13,500 s.h.p., were described in a paper read by sir john biles, and comparisons made on an economical basis with instal- lations of other types for the same vessels with diesel engines. when the difference in price between fuel oil and diesel oil is taken into consideration and also allowance made for the cost of lubricating oil for the diesel engines in excess of that for tur- bine, such proposals promise an economy in cost of fuel not in- ferior to that obtained with diesel engines, whilst they permit the use of either coal or oil as fuel. further the first cost of such an installation will be considerably less than the cost of diesel engines and little, if any, greater than that of a geared turbine installation of the usual design with low pressures and moderate superheat. birliography.—k. baumann, “ recent steam turbine prac- tice,’’ proc. inst. e. e., vol. 48, p. 768 (1912); *‘ some recent de- velopments in large steam turbine practice,” proc. inst. e. ef. {1921,;; hi. l. callendar, the properties of steam (arnold 1920); enlarged steam tables (arnold 1924);s. s. cook, ‘‘ steam turbines ”’ (howard lectures), proceedings r.s.a. (1923); ‘‘ the efficiency of marine auxiliary machinery,” section g., brittsh association at southampton 1925; also proc, inst. marine engineers (1926); r. dowson, “ maximum commercial efficiency of steam turbines,” world power (dec. 1923); w. j. goudie, steam turbines, 2nd ed. (longmans 1922); h. m. martin, ‘‘ a new theory of the steam turbine,” engineering, vol. 106, p. 11 (1918); hon. sir charles a, parsons, “ description of the compound steam turbine and turbo- electric generator,” proc. inst. m. e. (1888); lund humphries, “steam turbines,’ trans. world power conference, vol. 2, p. 1477 (1924); a. stodola, die dampfturbine, 6th ed., julius springer (berlin 1925); h. b. tostevin, “‘ experience and practice in mechan- ical reduction gears in warships,” trans. i.n.a. (1920); r. j. walker and $. 8s. cook, “ mechanical gears of double reduction for merchant ships,” trans. j.n.a. (1921); robert warriner, ‘ reduc- tion gears for ship propulsion,’’ trans. amer. soc. n.a. and m.e. (1921). (ry de ssr5. cy) turin, italy (see 27.418), the fourth city of italy, and the chief town of piedmont, is a flourishing and important industrial centre, with a population in 1921 of 502,274 (§17,140 including suburbs). the city has large motor car and artificial silk indus- tries. a fine monument to mazzini was erected in 1915 at the junction of the via pomba and the via andrea doria, and a memorial to italian cavalrymen to the east of the palazzo madama in 1923. turkestan or turkistan (see 27.419), the name applied to certain russian territories just east of the caspian. russian turkestan is divided between two independent socialist soviet republics, turkmenistan and uzbegistan, which, however, are constituent states of the u.s.s.r. turkmenistan (capital polterask, formerly called askabad, with a population of 33,636 in 1925) comprises all the territories west of the oxus and the south of the kirghiz a.s.s.r., and also a small strip of territory on the east bank of the river. uzbegistan (capital samarkand, 1 the relative commercial efficiency of internal combustion and steam engines for high-speed passenger vessels (trans. inst. naval arch., vol. 67, 1925). 843 with a population in 1925 of 72,370; largest town tashkent, with population of 263,871), comprises the territory between the oxus on the south, where it forms the afghan fronticr, turk- menistan on the west, the kirghiz a.s.s.r. on the north and the kara kirghiz autonomous province on the east. it includes nearly the whole of bokhara, and the districts of ferghana and samarkand. comprised within its territory is the autonomous socialist soviet republic of tadjikstan (capital durhambe). which forms the southeastern portion of uzbegistan. these administrative divisions correspond fairly accurately with the ethnographical distribution—the three republics being inhabited principally by turcomans, uzbegs and tadjiks respectively. according to estimates of 1925, turkmenistan had a population of 914,558, of which 79% were turcomans and 5% russians. its exact boundaries had not been delimited. uzbegistan had a population of 4,150,000, of which 3,575,000 were uzbegs, and an area of 184,800 sq. miles (250,000 versts). tadjikstan had a population of 609,000, of which 90% were tadjiks, and an area of 31,680 square miles... political history.—after the revolution of march 1017 the amir of bokhara asserted his independence and on april 20 granted a constitution; while the provisional govt. of russia convened an all-russian moslem congress in may 1917, which was eventually dissolved by the bolsheviks in may 1ror8. it appears to have achieved little. following the bolshevik revo- lution, a turkestan moslem congress proclaimed, in dec. 1917, the autonomy of turkestan and khokand, and established a provisional govt., which, however, was overthrown by the bol- sheviks in feb. 1918. by may the bolshevik forces had sur- rounded bokhara, and in august they had established them- selves in merv. in november “‘ white ” forces recaptured merv, only to lose it the following may, after which event a turkestan soviet govt. was formed, which in august sent a diplomatic representative to kabul. in sept. 1919 there was a successful anti-bolshevik rising in ferghana, which resulted in the forma- tion of a provisional govt., which lasted until feb. 1920. this month saw the consolidation of soviet power in turkestan; a rising in khiva resulted in the abdication of the khan, and by the end of the month only bokhara maintained a precarious in- dependence under the amir. a successful soviet campaign in august led to the establishment of the bokharan soviet repub- lic early in september. in the same month a treaty was signed with the republic of khwahrezm,which had been established after the capture of khiva, and a similar treaty was signed with bok- hara the following march. in april (1921) a decree of the all- russian central executive committee formally established turkestan as an autonomous republic. in march 1922 enver pasha began a campaign against the soviet forces in bokhara, and he was only finally defeated on june 26 at bairin; enver was assassinated in the following august in bokhara. thenceforward all organised opposition to the soviet adminis- tration ceased, though the basmachi, adherents of the ex-amir, continued to wage a guerilla warfare against the soviet authori- tics down to1925. in oct. 1923 khwahrezm was converted intoa socialist soviet republic by a congress sitting at kiev, and in oct. 1924 the republics of turkmenistan and uzbegistan were formally admitted to the union of socialist soviet republics. natural resources.—the climate of turkomanistan and western uzbegistan is very dry; rain only falls in the spring and cultivation has to be carried on almost entirely by artificial irrigation. the average summer temperature is 30° c., and for the year 17°c. the population is largely nomadic, though wheat, rice, cotton and fruit are grown. cotton planting has lately been intensively developed and large sums spent on irrigation; the area under cotton in 1926 has been estimated at 196,000 acres. crops of all sorts are, however, uncertain owing to irregular water supply and to the ravages of locusts. farther east the climate improves as country becomes more mountainous, and the uzbegs (nomads of mongol descent) breed horses, sheep, horned cattle and camels, and cultivate the river valleys. artificial irrigation is being developed; the area so watered in the oxus basin is to be increased from 405,000 ac. to over 3,000,000 by 1930 at a cost of £15,000,000. the area under cotton in 1926 had been increased to 1,515,000 acres. fruit is also grown for export. the mineral deposits are as yet undeveloped, but uranium ore is a . tm ? sent to kazan for the extraction of radium; coal, mercury, glauber’'s 844 salt, rock salt and naphtha have been located. silk weaving is still an important village industry. communications.—considerable developments in the communica- tions of central asia have taken place. the northern branch of the central asian railway has been extended from tashkent to pishpek and a further extension to alma-ata (formerly vyerni) has been begun. the southern branch has been extended along the oxus to termez and a further extension to dyushambe is in hand. the whole permanent way has been overhauled, and regular express services with dining and sleeping cars run to tashkent. load con- struction is also being taken in hand, and from march to oct. regular air services link up khiva, termez, dyushambe, pishpek, kagan and intermediate towns. bisl1ography.—a. j. toynbee, survey of international affairs 7920~3, pp. 428-445 (1925), and zd. 1924, pp. 217-228 (1926). these works give some further references to the little literature avail- able on this subject.