MATTER

since 1910 advances have been made which give much more precision to our knowledge of the consti- tution of matter. the atomic theory of matter, which for long appeared to be of necessity unverifiable by direct experiment on account of the minuteness of the atom (g. v.), received almost direct 835 proof in a number of ways. methods have been developed, for example, to detect the electrical effect of a single a particle from radium, and a single swift electron (see gases, electrical properties of). : the a particle has been shown to be a charged atom of helium projected with high velocity; the number of a particles from a given quantity of radium have been counted, and the volume of helium which they produce has been measured. in this direct way it has been shown that about 2-7 x10" particles or atoms oi helium are recuired to form one cu. cm. of helium gas at normal pressure and temperature. not only is it feasible to detect the effect of a single atom of matter in special circumstances but also to show the path of a swift a particle or electron through a gas. this has been made possible by the discovery of c. t. r. wilson that under suitable conditions the charged ions produced in gases by a or b rays become centres for the condensation of water vapours, and are thus rendered visible as the nuclei of visible drops of water. the photographs of these droplets show in a most striking way the track of the particle through the gas, and illustrate with extraordinary detail the main effects pro- duced by the passage of ionising radiations through gases. the essential correctness of the kinetic theory of matter, which assumes that the molecules of matter are in vigorous but irreg- ular motion, has been clearly demonstrated by the experiments of perrin and others on the motion and equilibrium of small spheres of matter in suspension in fluids which show the brown- ian movement. at the same time the atomic or discrete nature of electricity, which had been implicitly assumed in many theo- ries, has received complete experimental verification, and the magnitude of this fundamental unit of charge has been measured with precision. the most accurate experiments on this subject have been made by millikan by measuring the electric field required to support a small, charged droplet of oil or mercury. the charge on the drop was varied by ionizing the gas in its neighbourhood. in this way he has been able to show that the charge always varies by integral multiples of a fundamental unit. the charge given to a drop by friction or any other method is always an integral multiple of this unit charge. this fundamen- tal unit is the same both for positive and negative electricity, and is numerically equal to the charge carried by the negative elec- tron, the positive and negative ions produced in a gas by x-rays, and also to the positive charge carried by the hydrogen atom in the electrolysis of water. the magnitude of this unit charge, combined with electrochemical data, gives a most reliable method of measuring a number of important and molecular magnitudes. the value of the fundamental unit of charge and thus the mass of the individual atoms of matter are now known with an accu- racy of certainly within one per cent and possibly within one- tenth of one per cent. the data found by millikan are given in the following table:— fundamental unit of charge the avogadro constant, #.e., the nuniber of molecules in one gramme molecule ; , the number of molecules per c.c. of any gas at o°c. and 760 mms. # = 2-705 x 1079 mass of hydrogen atom in grammes m= 1-662 x 107*4 from these data the number of atoms in one gramme of any clement can be determined. while the average distance apart of the atoms or molecules can at once be deduced, the actual dimensions of the molecules or sphere of action of the molecules can only be approximately estimated with the aid of other and much less precise data. structure of the atom.—since the proof that the negative elec- tron of small mass is a constituent of all atoms of matter, there has been a vigorous attack on the fundamental problem of the structure of the atom. after passing through a number of phases the general ideas on this subject have crystallized into a fairly definite form, and it is now gencrally believed that the atom is composed of a massive positively charged nucleus of minute dimensions surrounded at a distance by a compensating distri- bution of negative electricity in the form of negative electrons. since electricity is atomic the resultant positive charge on the €=4:°774 x107" electrostatic units n=6:-062 x 1073 836 nucleus must be an integral multiple n of the fundamental unit of charge e and is given by ne. in order for the atom to be elec- trically neutral it must be surrounded by a distribution of nv negative electrons. the value of nv for each of the atoms is a fundamental constant, for on it depends the magnitude of the electric field surrounding the nucleus and the arrangement of the external electrons which in turn determine the main physical and chemical properties of the atom. the idea of the nuclear struc- ture of atoms arose initially from a study of the scattering of a particles in their passage through matter. on account of its great energy of motion the charged a particle penetrates the structure of some of the atoms and comes under the influence of the intense repulsive field of the nucleus. assuming that the law of force is that of the inverse square the a particle describes a hyperbolic path, and the angle of deflexion depends on the near- ness of approach to the nucleus. from a close study of the scat- tering of a rays by geiger and marsden it was concluded that the number of a particles scattered through diiferent angles was in close accord with the idea of the nucleus atom, while the actual number scattered through a given angle gave information on the magnitude of the charge carried by the nucleus. the pre- liminary experiments indicated that for the heavier atoms the value of v was about half the atomic weight in terms of hydrogen. t a notable advance was made by the fundamental experi- ments of moseley on the x-ray spectra of the elements. ile found that the x-ray spectrum was similar for all elements, and that the frequency of vibration of corresponding lines in the spectrum was proportional to the square of a number which varied by unity in passing from one element to the next. he concluded that the nuclear charge in fundamental units was equal to the atomic or ordinal number of the elements when ar- ranged in increasing order of their atomic weights. on this view the lightest element, hydrogen, has a nuclear charge 1, helium 2, lithium 3, and so on up to the heaviest element, uranium, of ordinal number 92. this is a generalisation of great importance and simplicity which has guided all subsequent work on the structure of atoms. the essential correctness of moscley’'s con- clusion has been directly verified in the case of a few representa- tive elements, by chadwick by accurate measurement of the nu- clear charge based on the scattering of a rays. moseley showed that with few exceptions all values of the nuclear charge between t and o2 were represented by known elements. moreover, when the atomic weight of the element in mendelceff's classification was replaced by its ordinal number certain irregularities were removed. for example, the positions of argon and potassium cobalt and nickel, iodine and tellurium were interchanged—a result in complete accord with their chemical properties (see chemistry). - the elements missing in the moseley classification were of atomic numbers 43, 61, 72, 73, 85, 87. since the x-ray spectra of these elements could be calculated with accuracy, it seemed likely that these missing elements, if present in appreciable quantity in the earth’s crust, should soon be detected. the first element discovered by its x-ray spectrum was number 72 which was called hafnium by hevesy and coster. in a similar way, elements of number 43, 75, have been recently found in certain platinum minerals by nonnack and tacke, but have not yet been isolated. thus the number of missing elements from hy- drogen to uranium is reduced to three, viz., numbers 61, 85, 87. it thus follows that the main physical and chemical properties of an element are defined by a whole number which represents both its nuclear charge in fundamental units and the number of external electrons. the atomic weight of an element is in a sense a secondary property, for, as we shall sce, elements can exist of the same nuclear charge but of different atomic weights. the number and position of the external electrons, on which the ordi- nary chemical and physical propertics of an atom depend, are defined by the nuclear charge. the mass of the atom which resides mainly in the nucleus exercises a subordinate effect on the external arrangement of the electrons. isotopes (g.v.).—on moseley’s classification only 92 elements of ordinal numbers 1 to 92 are possible, assuming that uranium matter (92) is the last of the elements. we shall now briefly discuss some recent advances which clearly show that in some cases several elements can exist with the same nuclear charge but of different atomic masses. information on this point was first ob- tained from a study of the radioactive bodies. it was early ob- served that a number of products which showed different radio- active properties were inseparable from one another by ordinary physical and chemical methods. for example, ionium and thor- ium, radium and mesothorium, radium d and lead cannot be separated from each other, and appear to be identical in chemical properties. elements so closely alike in chemical properties were called “isotopes ’’ by soddy, since they appeared to occupy the same position in the periodic arrangement of the elements. viewed from the standpoint of the nuclear theory isotopes are elements of the same nuclear charge but of different atomic masses. as we have seen, the nuclear charge controls the ordi- nary physical and chemical properties of the atom, and the mass which resides almost entirely in the nucleus has only a second- order effect. on the other hand, the property of radioactivity depends on the structure and stability of the nucleus, which may be very different for atoms of the same resultant nuclear charge. in the article on radioactivity attention is drawn to the remarkably simple relation which exists between the chemical properties and radiations of the series of radioactive elements. with the aid of this relation we can at once write down the ordi- nal numbers and masses of the long series of elements which arise from the transformation of uranium, thorium and actinium, and can follow the origin of the numerous isotopes which arise. one of the most striking results of this generalisation was the pre- diction that the end product of the uranium and thorium series should be an element of the same ordinal number as lead but of atomic masses 206 and 208 respectively, instead of the mass 207 found for ordinary lead. this result has been directly confirmed by atomic weight determinations of uranium-lead and thorium- lead, and was the first definite proof of the existence of isotopes of a non-radioactive element. it seemed probable that in a similar way many of the ordinary elements might consist of a mixture of isotopes, 7.e., elements with the same nuclear charge but different atomic masses. this has been confirmed in a number of cases chiefly by the work of aston. the masses of the positively charged atoms present in the electric discharge in a vacuum tube are examined by bending the rays in a combined magnetic and electric field. in this way it was found that neon consisted of two isotopes of masses 20 and 22 and chlorine of isotopes of masses 35 and 37. the relative proportions of the two isotopes in chlorine was in good accord with that to be expected from the ordinary atomic weight of the mixture of isotopes, v1z., 35°45. this new method of analysis had, up to 1925, been enpioved for more than half of the elements and had yielded results of great interest. some of the elements, like carbon, nitrogen and oxygen, give no isotopes, and are thus to be regarded as “ pure ”’ elements where the atoms have all the same mass and nuclear charge. others, like chlorine, argon, krypton and mercury, are composed of a mixture of two or more isotopes. in cases like krypton and mercury as many as six well-defined isotopes have been detected. with few exceptions the masses of all the tso- topes are expressed by a whole number in terms of o= 16 with an accuracy of about 1 in 1,000. for example, the isotopes of neon are 20:00 and 22-00. this important cenclusion, which has been verified in a number of cases, affords a strong indication that the masses of the parts composing the nucleus have a mass either of one or a multiple of one, and are not direct multiples of the mass of the hydrogen atom which is 1-008 where o= 16. the reason of this will be discussed later. in a few cases, how- ever, for example tin and xenon where the isotopes can be ob- tained together on the same record, aston has pointed out that the whole-number rule obviously breaks down. it will be of great importance to determine the mass of all the isotopes with the greatest exactitude as the departure of the masses from whole numbers may provide valuable information on the struc- ture of atomic nuclei. matter while the ordinary physical and chemical properties of iso- topes are closely similar, it is to be expected that they should differ in all qualities which involve directly the mass of the atom, e.g., the coefficients of diffusion and specific gravity. in a similar way second-order effect is to be expected in the rate of vibration of the external electrons, 7.e., in the light spectrum of the ele- ment, and a small effect has been observed in several cases. the most obvious method of partial separation of isotopes is by the process of diffusion or evaporation. in this way a partial sepa- ration into light and heavy fractions has been shown in the case of neon, mercury and chlorine. no evidence of the separation of isotopes in nature has been so far observed except in the case of uranium-lead and thorium-lead already referred to. for example, chlorine obtained from widely different sources shows no difference in the relative proportions of its component isotopes. distribution of electrons.—-we have seen that the atom is to be regarded as an electrical structure in which a positively charged nucleus is surrounded by a number of electrons. the magnitude of the nuclear charge and the number of the external electrons are known for each of the elements. in considering the distribution of the external electrons round the nucleus, we are at the outset faced by the great difficulty that no possible arrangement can be permanently stable on the basis of the class- ical dynamics. for example, an electron in motion round the nucleus must on the classical theory radiate energy and fall into the nucleus. to overcome this fundamental difficulty bohr has introduced a conception, based on the quantum theory (@.2.), in which radiation only occurs in definite quanta. this concep- tion further developed by sommerfeld and others has been al- most completely successful in describing the properties of the simplest atom (hydrogen) with only one electron. it yields not only its natural frequencies but also the detailed changes which they undergo under the influence of electric and magnetic fields. in atoms with more than one electron, success has so far been less complete. this is probably not entirely due to the mathe- matical difficulties of the classical problem of three or more at- tracting bodies (almost insuperable as these are) but even more to deep seated inadequacies in the modifications of classical theory required by atomic theory. the simple modifications introduced by bohr with success for hydrogen await further development. in spite of this, however, the theory in its present form has already won marked successes. it has accounted suc- cessfully for the general structure of the spectra of all atoms and their resemblances to the spectrum of hydrogen, for the general arrangement and actual magnitudes of their x-ray spectra, and for the close analogies which these exhibit to optical spectra. it has enabled the grouping of the electrons in all atoms to be determined, with rough estimates of the size of the orbits to which they are confined. the later developments of the theory (main-smith, stoner) seem to present the details and subgroups of electrons in the atom with some approach to finality, in har- mony with all the physical and chemical evidence. the theory has succeeded in accounting naturally for the form of the periodic table of the elements, especially the occurrence of the transition groups of elements ending at copper, silver and gold, and for the occurrence of the chemically similar rare-earths. it has therefore already played a great part in the simplification and co-ordination of facts of value. its developments scem likely to supersede suggestions as to the grouping of the electrons in the atom which have been advanced previously from time to time—notably by kossel, lewis, langmuir, j. j. thomson, with certain measures of success in explaining the periodic table of the elements and the methods of chemical combination. these earlier theories were, however, for the most part descriptive rather than qualitative in character—to a far greater extent than the theory initiated by bohr. the whole problem of the distribution and motion of the electrons in a complex atom is a very difficult one. while definite progress had been made by 1921, and great advances between 109021 and 1925, much still remains to be done before we can hope to specify with any degree of quantitative completeness the motion, position and mode of vibration of the electrons in any atom of two or more electrons. 837 siructure of the nucleus. —while it is difficult to estimate the dimensions of atomic nuclei, the general evidence indicates that the nucleus of a heavy atom like uranium, if assumed spherical, has a radius of less than ro~tm cm. or less than 1/1000 of the radius of the external atom. no doubt the dimensions of a nu- cleus depend on its complexity and are much smaller for the lighter atoms. irom experiments on the passage of a particles through hydrogen, it has been calculated that the dimensions of the helium nucleus of mass 4 is of the order 10 !? centimetres. the most direct evidence on the constitution of the nucleus is derived from the study of the radioactive transformations. the disintegration of an atom is accompanied either by the expulsion of an a particle, 7.e., in helium nucleus, or the release of a swift electron from the nucleus. this shows that the nucleus of the radioactive atoms contains both positively charged masses and negative clectrons, and that the nuclear charge represents the resultant charge. it is natural to conclude that the helium nu- cleus of mass 4 1s one of the secondary units which make up the structure of a complex nucleus. this is supported by the obser-_ vation that the atomic mass of many atoms is expressed by 4". where # is a whole number. it is clear, however, from the work of aston on isotopes that, in addition to the helium nucleus, an element of mass 1 or integral multiple of 1 enters into the struc- ture of all nuclei. this fundamental unit of structure has been named “ proton,” and its atomic mass is 1 or very nearly 1 in terms of o=16. on this view the nuclei of all elements are made up of positively charged protons and electrons. the mass of the atom measures the number of protons in the nucleus. this is in a sense a return to the famous hypothesis of prout according to which all the atoms are supposed to be built up of hydrogen as the fundamental unit. it seems clear that if a proton could be removed from an atomic nucleus it would prove to be the hydrogen nucleus carry- ing a unit positive charge. in fact, rutherford and chadwick have shown that the hydrogen nucleus can be liberated from certain light atoms by bombardment with swift a particles. it remains, however, to explain why the proton in a nucleus has a different mass from the free hydrogen nucleus. the latter has a mass 1-008 in terms of o=16 while the proton in the nucleus has a mass unity, or nearly unity. while the negative unit of electricity exists in the form of the electron of very small mass, no evidence has been obtained that its counterpart, the positive electron of very small mass, exists. the unit of positive electricity has never been found to be asso- ciated with a mass less than that of the hydrogen atom. this has led to the view that the hydrogen nucleus is the positive electron, and that its mass is about 1,845 times that of the nega- tive electron. this difference in mass between the units of posi- tive and negative electricity appears to be fundamental, and offers an explanation of the asymmetrical distribution of positive and negative electricity in the structure of atoms. since the helium nucleus has a mass 4 and charge 2, it should be composed of four hydrogen nuclei and two electrons. its mass, however, is less than that of four free hydrogen nuclei. such a change of mass in the very close combinations of positive and negative nuclei is to be expected. according to the theory of relativity energy has mass, and the loss of mass m of a system is numerically given by l=mec? where j: is the energy liberated and ¢ the velocity of light. on this view the combination of the positive and negative electrons to form the helium nucleus is accompanied by a large release of energy. from the difference between the mass of the helium nucleus and that of four hydro- gen nuclei, it can readily be calculated that the helium nucleus is such a stable combination that an amount of energy corre- sponding to four or five a particles from radium would be required to dissociate it. the difference between the masses of the pro- tons in the nucleus and free hydrogen nuclei is thus to be ascribed in general to the close packing of the positive and negative units composing the nucleus. on the views outlined above the number of electrons in any nucleus can at once be calculated. for example, oxygen of nuclear charge 8 should be made up of 16 positive units and 8 3 838 electrons. for such a nucleus to hold together it seems clear that the forces between the charged units at such small distances must be different from that of the inverse square. while it has been experimentally shown that the law of the inverse square holds at any rate approximately close to the nucleus of a heavy atom like gold, this law breaks down in very close collisions of light atoms where the nuclei approach very close to each other. for example, it has been found that the number of hydrogen atoms which are set in swift motion when a particles pass through hydrogen is very different from that to be expected if the nuclei behave as point charges repelling each other according to the law of the inverse square. by studying the scattering of a particles by the light elements, aluminium and magnesium, it has been found that the law of the simple inverse square no longer holds close to the nucleus. ‘the experimental information at present available is too indefinite to hazard more than a guess as to the nature and magnitude of the forces that come into play when nuclei approach very close to one another, as they must do in the structure of the nucleus of a heavy atom. stability of atoms —apart from the heavy radioactive ele- ments which belong to a class by themselves, and two other elements—potassium and rubidium—which spontaneously emit swift electrons, the atoms of the ordinary elements appear to be very stable structures which cannot be broken up by ordinary chemical and physical agencies. in considering the possibility of the disintegration of elements it should be borne in mind that the loss of one or more electrons from the outer electronic system has no permanent effect on the atom, for other electrons ulti- mately fall into the atom to fill their place. in order to produce a permanent transformation of the atom it appears necessary to remove a positively charged particle or an electron from the nucleus of the atom. this can only be effected by agencies which are able to penetrate the nucleus or to pass very close to its structure. a number of experiments have suggested that possibly helium and hydrogen may be liberated by the passage of an electric discharge through gases, but on account of the presence of these elements in many materials it is difficult to prove defi- nitely that they arise from artificial transformation. during the last few years there has been a vigorous attack on the question whether transformation of nuclei can be effected by the action of intense electric discharges through gases or vapours. by pass- ing a heavy current through mercury vapour, it is claimed that gold is produced in appreciable quantity. by a similar mode of procedure it is stated that lead can be converted into mercury, for obvious reasons, it is very difficult to be certain that the ele- ments observed were not originally present in some form in the material subjected to the electrical discharge. in the cases men- tioned above, we should have expected that the gold or mercury would have a different atomic weight from ordinary gold but definite evidence on this point is not yet available. the whole question whether transformation of atomic-nuclel can be pro- duced insuch a comparatively simple way and on such a largescale is still sub judice. the energy of the electrons in the discharges used is in general small compared with that of the @ particle, with the aid of which transformations on a minute scale were first shown. the a particle expelled from radium is one of the most con- centrated sources of energy known to us, and on account of its speed should be able to penetrate the structure of the nuclei of many of the lighter atoms, and still retain sufficient energy to disrupt the bonds that hold the parts of the nucleus together. in the case of an atom of high nuclear charge the a particle may lose so much of its energy in approaching the nucleus that it may be unable to effect its disintegration. it has been found that when a particles pass through hydrogen or any material containing combined hydrogen, some of the particles pass so close to the hydrogen nucleus that they set it in swift motion. these swift hydrogen atoms can be detected by the scintillations they pro- duce on a zinc sulphide screen. this is purely a case of colli- sions of atomic nuclei, and the speed of the h atom set in matter motion can be calculated by the ordinary laws of mechanics. the maximum range or distance of penetration of such a particle is about four times that of the incident a particle. in a similar way other nuclei must be set in swift motion by their collision with a particles, but it can be calculated that in most cases such nuclei are unable to travel as far as the a parti- cle, and thus remain undetected amid the great number of inci- dent a particles. rutherford showed that when a strong beam of a particles passes through oxygen or carbon dioxide, only a few h atoms of a penetrating type are present and these appear to have their origin in the radioactive source. when, however, the rays pass through dry nitrogen, a much larger number of penetrating particles is observed. by bending these particles in a magnetic field, it is clear that these swift particles are not charged atoms of nitrogen but projected hydrogen nuclei. these h particles are detected by the scintillations they produce in falling on a screen of zinc sulphide, and progress in this line of work has been much facilitated by the designing of special counting microscopes of wide aperture which have a large field of view. rutherford and chadwick found that in addition to nitrogen, swift h parti- cles are liberated from boron, flourine, sodium, aluminium and phosphorus. by a variation in the method, similar h particles, but of lower speed, were observed from neon, magnesium, sili- con, sulphur, chlorine, argon and potassium. kirsch and petter- son claim that h particles are also liberated from carbon and oxygen, but this question is still sub judice. it seems clear that these h particles are liberated from the nuclei of these elements by the bombardment of a particles and in @ sense we may say that these nuclei have undergone a nuclear transformation with the ejection of a proton at high speed. for elements like b, n, na, al, p, the velocity of expulsion of the h particles is in all cases greater than that for a free h atom in a close collision with an a particle. for example, using a particles of range 7-0 cm. in air, ordinary ii atoms can not travel further than 30 cm. of air. on the other hand, the h particles liberated from nitrogen travel 40 cm. and from aluminium 90 cm. it is thus certain that th particles observed from the elements given above cannot be due to the presence of ordinary hydrogen as an impurity. in the case of aluminium, a few of the h particles are released with more energy than that of the a particle which effects their release. no certain evidence has yet been observed that other types of particles are set free in these disintegrating collisions. it might have been expected that nuclei of mass 2 or 3 or 4 should also appear in some cases, as there is some evidence that secondary units of this kind go to build up atomic nuclei. it is of interest to note that the protons set free by the a par- ticles appear to be ejected equally in all directions, although their speed is somewhat greater in the forward direction of the a par- ticle. this difference is no doubt due to the fact that the bom- barded nucleus is set in motion by the collision. {t is difficult to be certain of the mechanism of these collisions and in particular whether the bombarding a particle is captured by the nucleus when the proton is hberated. by photographing several hundred thousand tracks of a particles in nitrogen by the wilson method, blackett has observed a number of collisions, involving the escape of a high speed proton. there is, however, no trace of the a particle after the collision, indicating that it is captured by the nucleus. if this be the case, the nucleus gains ana particle of mass 4 and loses a proton of mass 1. no definite evidence of the mechanism of the collision is as yet available for the other “ active ”’ elements. it should be borne in mind that the disintegration observed in this way is on an exceedingly small scale. not more than ro particles in a million get sufficiently close to a nucleus to release an h atom. it seems clear, however, that while the ordinary atom is undoubtedly very stable, its disintegration can be brought about by the aid of sufficiently powerful agencies which are able to penetrate its structure. as already pointed out, there are strong reasons for believing that the helium nucleus is a very stable structure which cannot be broken up even by the swiftest a particle at our disposal. maude—mauritius while it is reasonable to suppose that all the elements have been built up by combinations of protons and electrons, there was in 1925 little evidence to throw light on the conditions neccs- sary to lead to the formation of complex nuclei. no doubt, how- ever, this process of aggregation has gone on in the past, and may still be in progress under favourable conditions, if not on this earth, at any rate in some of the stars. (e. ru.) maude, sir frederick stanley (1864-1917), british soldier, son of gen. sir frederick maude, v.c., was born at gibraltar june 24 1864. he entered the coldstream guards in 1884, took part in the suakin operations, 1885, and joined the staff college in 1895. in the south-african war, as brigade- major of the guards brigade, he took part in the advance to pretoria. after a spell in canada as military secretary to the governor-general, he took an active part in the development of the organisation and training of the new territorial force. on mobilisation in aug. 1914 he was posted to the staff of the iii. army corps and served in france until june 1915. in aug. he was hurried out to the dardanelles to take up command of the 13th division. there he played a conspicuous part in the evac- uations of suvla and of helles, and in 1916 his division was dis- patched from egypt to mesopotamia to aid in the relief of kut- al-imara. they arrived in time to bear a share in the final desperate endeavours to save the doomed stronghold, but the effort came to naught and after the surrender of kut-al-imara, maude and his division remained facing the turks on the tigris. he was advanced in sept. to the position of army commander in mesopotamia. realising that victory in this theatre of war must hinge on effective organisation and adequate preparation, maude spent three months at basra, ensuring that when the time came his field army should be capable of acting with vigour and decision. then, when all was ready early in dec., he suddenly pushed forward and within a few weeks had driven the turks in con- fusion out of their entrenched camp around kut. moving re- lentlessly on, and making great captures, he occupied baghdad march rr. he spent the next few months consolidating his position and preparing plans for a fresh offensive. he was, however, struck down by cholera, and died at baghdad nov. 18 1917. his conquest of mesopotamia and his transformation of a depressing situation into one of signal triumph ranks as one of the finest feats in modern military history. (see mesopotamia, operations in.) see maj.-gen. sir c. e. callwell, life of sir stanley maude (1920). maunoury, michel joseph (1847-1923), french soldier, was born at maintenon (eure-et-loir) dec. 11 1847. com- missioned to the artillery from the ecole polytechnique in 18609, he saw service in the franco-german war, and in 1883 was placed on the staff at the military school of st. cyr. he retired in 1912, having been military governor of paris and a member of the conseil supericur de la guerre. on aug. 19 1914 he was given charge of the army improvised in lorraine from the reserve divisions, and was entrusted with the investment of metz. on aug. 24 he made a brilliant attack on the left flank of the v. german army; and when, on aug. 26,a new vi. army was assembled on the somme, the command was given to gen. maunoury. it was this army, which, on sept. 4, was launched against the flank of von kluck’s i. army—an action which opened and exercised a decisive influence on the battle of the marne. maunoury continued to command the vi. army throughout the development of the aisne line of battle and in the early phases of trench warfare. on march 15 1915 he was severely wounded, and thereafter held no active command. from nov. 1915 till march 1916 he was governor of paris. he died on march 28 1923 and was created marshal of france post- humously. maura, antonio montaner (1853-1025), spanish states- man, was born in palma de mallorca may 2 1853. he was educated at valencia and madrid where he studied law. though his pronunciation of spanish was first defective, by perseverance and force of personality he became in later years a great forensic and parliamentary orator. elected deputy for his native city 839 in 1881, he joined the liberal party; but his instincts were conservative and in roor he went over to the conservative party of which he eventually became leader. he was a con- structive statesman, and though the chaotic state of the spanish political fabric inspired in him a desire for reform, he always regarded the constitution as sacred. in 1903 he became prime minister, and his zeal for reform made him many enemies among the corrupt political factions of spain. he negotiated with france on the subject of spanish rights in tangier and morocco and with great britain concerning the sfafus quo of the seas. in 1913 he resigned the leadership of the conservative party, but, in response to appeals from the king, he formed governments in 1918, t919 and 1921. true to his constitutional ileals, he refused to make common cause with the directorate of 1923 which superseded parliamentary government in spain. he died dec. 13 1925. maurel, victor (1848-1923), french singer (see 17.907), died in new york oct. 23 1923. maurice, sir frederick barton (1871- ), british soldier, was born feb. 1 1871, and was commissioned in the sherwood foresters (notts. and derby regiment) in 18092. he saw service in the tirah campaign 1897-8 and the south afri- can war 1899-1900 and from 1904 until 1914 held a series of gen- eral staff appointments, the last year as instructor at the staff college. on the outbreak of the world war he was appointed general staff officer (1st grade) to the 3rd div., british expedi- tionary force. he became brigadier-general, general staff, in 1915 and the same year he was advanced to the post of director of military operations at the war office. here he was, during the middle period of the war, the intimate and valued assistant of sir william robertson, until the latter’s resignation early in 1918. after the spring disasters maurice wrote a letter to the press chal- lenging the accuracy of ministerial statements, considering them an attempt to shift the responsibility on to the army when several hundred thousand troops were retained in england to guard against a hypothetical invasion. by this act of moral courage he fulfilled his sense of honesty at the sacrifice of his ca- reer. retired for the breach of discipline he became a military correspondent, and after the war, as principal of the working men’s college, st. pancras, london, and vice-president of the british legion, was prominent in social work. his publications include forty days in rorq (1920); lord wolseley (with sir george arthur, 1924); robert e. lee, the soldier (1925). (see western front.) mauritania (sce senegal, 24.643).—this region of french west africa, between the senegal river and rio de oro, was con- stituted a colony in 1921. the area, including saharan regions, is 154,000 sq. miles. the population, mostly moors, 7.e., tribes of mixed berber and arab descent, is 280,000. port etienne, on levrier bay, cap blanc, created since the occupation of the country by the french, is the seat of a growing fishing industry.