COLLOIDS

in the course of investiga- tions (1861-4) on the diffusion of substances in solution, t. graham, professor of chemistry in university college, london, and master of the mint, found that certain substances, e.g., sugar and common salt when in solution, can pass through or diffuse through a membrane of parchment paper, whereas other substances, e.g., starch and gelatin, cannot do so. since the substances which could pass through the membrane were such as generally crystallise well, whereas those which did not pass through were, as it was thought, non-crystallisable and of a gelatinous nature, graham divided substances into crystalloids and colloids (from the greek xeadaa, glue). although this distinction was for long maintained, more recent investigation has shown that graham’s classification is unsuit- able; and the terms crystalloid and colloid are now no longer employed to connote different kinds of substances but only different states or degrees of sub-division of matter. ina solution of cane sugar, for example, molecules of sugar are distributed homogeneously throughout the solution, or, as it is said, the sugar is molecularly dispersed. in the case of gelatin and other so-called colloids, the substance does not exist in the molecular but in a coarser state of aggregation. the particles, however, are too small to be seen by the ordinary methods of microscopic examination. in short, the term “ colloid ” or ‘‘ colloidal state’ is now used to connote a state or range of sub-division of matter lying between the limits of the microscopically visible and the molecular states. these limits may be taken as, approximately, one ten-thousandth of a millimetre (0-1 #) and one-millionth of a millimetre (1 py). although graham’s classification of substances into crystal- loids and colloids was imperfect, the process of dialysis which he introduced gave a means, still universally employed, of dis- tinguishing between molecularly dispersed matter and matter in the colloidal state. by a refinement of the process, it is possible, using collodion membranes of varying permeability, to separate colloids of different degrees of dispersity. gencral properties—since the peculiar and characteristic prop- erties of the colloidal state do not depend on the physical state of the finely sub-divided matter or of the medium in which the matter is dispersed, colloidal properties are exhibited both by colloidal suspensions and emulsions (solid particles and liquid droplets dispersed in a liquid medium), and by smokes and mists (solid particles and liquid droplets in a gaseous medium), foams (gas bubbles in a liquid dispersion medium), and so on. whilst it could be inferred from the experiments of graham colloids that the colloidal systems, although apparently homogeneous like a solution of sugar, are nevertheless heterogeneous or contain particles which have a magnitude greater than molecular, the actual existence of such particles is rendered evident by the scattering of light which they bring about (the so-called tyndall effect). the introduction of the ultramicroscope by siedentopff and zsigmondy enables the eye to detect the presence of particles of a magnitude of about six millionths of a millimetre, about sixty times the dimensions of a hydrogen molecule. dispersion of light.—in the scattering of light by finely divided particles, the light of shorter wave length is scatteredl most, and the light which reaches the eye is therefore blue or bluish in colour. consequently, a system containing colloidally dispersed particles, when illuminated from the side and viewed against a dark background, will appear blue. as leonardo da vinci suggested long ago, we can, in this way, explain the blue- ness of the sky as due to the scattering of the sunlight by finely dispersed particles in the atmosphere; or, as is now thought, by the molecules of the atmospheric gases themselves, the back- ground being the blackness of infinite space. the blue colour of the eye and the colour of many feathers also find their explana- tion in the scattering of light by finely dispersed matter. surface changes and adsorption.—since the colloidal state is a state of very fine sub-division, the extent of surface exposed is very large relatively to the total volume of the matter. surface forces, consequently, play a predominant part and bring about changes in the distribution or concentration of matter at the surface of the particles. this change of concentration at a sur- face, brought about by surface forces, is spoken of as adsorption, a phenomenon readily observed in the decolourisation of liquids and the removal of noxious or obnoxious gases by the very porous, and therefore surface-active, material, charcoal. in the production and characterisation of colloidal systems, adsorption plays a part of the highest importance. by the ad- sorption of ions from the dispersion medium or from electro- lytes present in solution, the colloid particles acquire an electric charge. adsorption of the dispersion medium as a whole may also take place to a greater or less extent, whereby variation in the general behaviour of colloids may be brought about. in the case of the so-called suspensoid or hydrophobe (or, generally, lyophobe) colloids, the dispersed particles may adsorb none or practically none of the dispersion medium; and they exist, there- fore, in suspension as non-hydrated or non-solvated particles, the stability of which is due mainly to their electric charge and to their brownian movement. in the case of the so-called emul- soid or hydrophile (lyophile) colloids, such as solutions of gelatin or of starch, adsorption of the dispersion medium itself takes place, and the stability and properties of such a colloidal solution (colloidal sol), are due to the adsorbed dispersion medium as well as to electric charge on the particles. the greater the extent to which the adsorption of the dispersion medium takes place, the more will the stability and properties of the colloid be dependent on the adsorbed medium and the less will they depend on the electric charge. electrolyies.—ilf the electric charge on a suspensoid colloid be neutralised, agglomeration of the particles followed by precipita- tion takes place, and this neutralisation of the electric charge can readily be effected by the addition of electrolytes. negatively charged colloid particles will preferentially adsorb the positive ions of the added electrolyte, and positively charged colloids will preferentially adsorb the negative ions, the charge on the colloid being thereby neutralised. although multivalent ions are, in gen- eral, more effective in producing precipitation than are univalent ions, recent investigation shows that there is no exact relationship between the valency of an ion and its precipitating power, and that the adsorbability of the ion may exercise an important influence. natural electrolytes—the precipitation of fine particles by electrolytes is well illustrated on a large scale in nature, the finely divided clay carried by many rivers being caused to deposit when the river water mingles with the sea. in this way the silting up of river mouths and the formation of deltas, as in the case of the nile and of the mississippi, are brought about. 675 the electrical charge on a colloid particle may also be neutral- ised by another colloid carrying an electric charge of opposite sign. colloids of opposite sign may mutually precipitate each other and give rise to “‘ adsorption complexes ” which simulate chemical compounds. purple of cassius, for example, is an adsorption complex of stannic oxide and colloidal gold. action on solutions.—in the case of solutions (or sols) of hydrophile (lyophile) colloids (e.g., gelatin}, the stability of the colloid is due mainly to adsorbed water or other dispersion medium, and consequently such solutions are not so sensitive to added electrolytes. even though the addition of small amounts of an electrolyte may produce changes in the amount of water adsorbed by the colloid, actual precipitation does not take place until the concentration of added electrolyte is relatively jarge. the relatively great insensitiveness to electrolytes which is shown by hydrophile colloids may be transferred to hydrophobe colloids or suspensoid colloids. when gelatin, for example, is added to a colloidal gold sol, the gold is adsorbed by the gelatin and a much greater concentration of electrolyte is required in order to precipitate the gold than is necessary in the absence of the gelatin. the gelatin is said to protect the gold, and this so- called protective action, which varies greatly in the case of different hydrophile colloids, is of much importance in many directions (see electro-metallurgy). gelatin types.—many colloids of the hydrophile type exhibit, when cooled, the property of passing into a jelly by a coalescence of the hydrated colloid particles. the jelly so formed may be dried to a more or jess hornlike material, such as ordinary dry gelatin. these jellies have the important property of taking up or imbibing water, even against very great pressures. the amount of water imbibed is greatly affected by the presence of electrolytes, being increased by acids and alkalies, up to a cer- tain concentration; but the increased swelling produced by dilute acids is diminished by the addition of salts. the properties of colloid matter play a part of the greatest importance not only in physical but also in biological science. in agriculture, the presence of colloids in the soil is of importance by their water-retaining power and by their power of adsorbing salts and plant foodstuffs and of retarding the washing away of these materials by rain. colloids in industry—adsorption, also, plays an important part in the dyeing of textiles and the staining of animal tissues. the negatively charged colour ion of the acid dyes will be pre- dominantly adsorbed by a positively charged fibre, and a posi- tively charged dye (basic dye) will be predominantly adsorbed by a negatively charged fibre. after the dye has been adsorbed, secondary changes may take place, leading to the formation of a more stable adsorption complex (see dyeing). by the use of “ protective” colloids, sparingly soluble sub- stances produced in chemical reactions can be kept in a colloidal state and so prevented from undergoing flocculation and sedi- mentation. in the production of the photographic plate, the silver bromide, formed by mixing silver nitrate with potassium bromide, is prevented by the gelatin from forming a precipitate of coarse particles unsuitable for photographic purposes, and is kept in a finely divided form. in normal bile, the bile salts, albuminoids, etc., act as protective colloids which keep the sparingly soluble substances, such as cholesterin and the calcium salt of bilirubin, in the colloidal state and so prevent their deposi- tion; but when a reduction of the amount of protective colloids is brought about by pathological conditions, deposition of the sparingly soluble substances takes place in the form of gall- stones (see b1o-chemistry). colloids in afiik.—the nature of the curd which separates from milk and the readiness with which it is formed are greatly affected by the presence of protective colloids. in cow’s milk there is a relatively large amount of casein and a relatively small amount of the protective colloid, lactalbumin. cow’s milk, therefore, readily curdles. in human milk there is a smaller proportion of casein and a larger proportion of lactalbumin; the casein is therefore more effectively protected and curdling takes 676 nlace less readily. in asses’ milk, the relative proportion of pro- tective colloid is highest of all and curdling takes place with greatest difficulty. the digestibility of asses’ milk is conse- quently greatest. by increasing the amount of protective colloid in cow’s milk through the addition of gelatin or white of egg or of barley water (starch), curdling is caused to take place less readily and the digestibility of the milk is increased. the living protoplasm (see cyrolocy) of the animal or vege- table cell, finally, is a complex system of colloids in which there occur processes of adsorption, changes of dispersity, altera- tions in the distribution of water between the colloidal particles and the dispersion medium, a system in which the mutual rela- tions between the colloids are in a constant state of flux. only in such a colloid system ts it possible ta have the flexibility and adaptability to the varying requirements of what we call life and growth. moreover, the many diverse chemical reactions involved in breaking down complex foodstuffs into simpler sub- stances and building up again these simpler compounds into the complex proteins of the protoplasm are accomplished in the living body under the catalytic activity of the enzymes, and these are themselves colloidal. the living organism, therefore, is a vast colloidal community, the diverse members of which are held together in common service by surface forces and by mutual actions and reactions of electrical charges. in this com- munity the colloidal workers are engaged in carrying out the multifarious and complex chemical operations on which the life and the health of the community depend. (aas) collyer, robert (1823-1912), american divine (see 6.694), died in new york city nov. 30 rgr2. colman, samuel (1832-1920), american landscape painter (see 6.695), dicd in new york city march 27 1920. cologne (ger. kgln sce 6.697), the third city of germany, had a population in 1925 of 693,266, including miilheim, mei- heim and worringen (with a population of 84,000) incorporated in the city in 1914. cologne is an important commercial centre and is the retail town for the industrial cities of the rhineland and westphalia. the first international cologne fair was held in 1924. the city is now visited again by numbers of tourists. cologne was one of the chief military centres of germany during the world war, and was bombed in 19t7 and 1918. the allies occupied the city and a bridgehead of 18 sq. m. on the other bank of the rhine under the terms of the armistice. the cologne zone was to be evacuated after five years 1f germany fulfilled her obligations under the treaty. it was formally entered, in dec. 1918, by sir. h. plumer’s army, and formed the head- quarters of the british army of occupation. the evacuation was postponed owing to the report of the inter-allicd commission of control that germany had not fulfilled her obligations with respect to disarmament, but it was finally evacuated on jan. 30 1926. the great bell of the cathedral, weighing 27 tons, was melted down during the war, and a new one was dedicated in 1924 (see also rhineland). colombia (see 6.700), a republic in south america and a mem- ber of the league of nations. its area is 462,024 sq. miles. at the census of 1918 the population was 5,855,490. in 1925 it was esti- muted to be 6,617,833, about half being whites or of mixed blood. y. political history on aug. 3 1909, gen ramon gonzflez valencia was elected by congress to serve as president for one year in place of gen. rafael reyes. the latter’s dictatorial rule had aroused popular indignation, and after two terms as president he left the country. gonzalez-valencia found the country suffering from bad ad- ministration, and still feeling the disturbing effects of the civil war of 1899-1902, and the secession of panama. on july 15 tg10, dr. carlos e. restrepo was inaugurated as president, after a formal election, and more stable conditions prevailed. the law of 1906 for the representation of minorities in congress and other public bodies came into effect, and its application, even to the appointment of judges and other oftfice-holders, led to the co-operation of all parties in the pacification and good govern- ment of the republic. the law of 1898, guaranteeing the liberty collyer—-colombia of the press, had been disregarded under the revime of gen. reyes, but after 1910 it was rigorously observed. the movement toward currency reform and financial stability was also begun, and further efforts were made toward a settlement of differences with panama and the united states arising out of the secession of the former from colombia and its constitution as an inde- pendent republic. relations between the three countries had long been delicate. the visit of gen. reyes to washington had proved futile, and the treaty negotiated in r909 between co- lombia’s envoy, e:enrique cortes, and the u.s. secretary of state, elihu root, dul not: prove acceptable to colombia. at the regular presidential election in feb. 1914, dr. jose vicente concha, the conservative candidate, was returned. he had the support of the liberal party, and in the formation of his cabinet he filled some of the offices with liberals, thus inaugu- rating a coalition form of government and fulfilling the spirit of the minority representation law. during 1914 renewed efforts were made to adjust colombia’s differences with panama and the united states, and on april 6 a treaty was signed by thad- deus a. thompson, u.s. minister at bogot&, and francisco j. urrutia, colombian minister of foreign relations. this treaty was ratified by congress on june 9 1914, but did not obtain approval by the u.s. senate ull seven years later, nor come into final effect without prolonged negotiations. president concha was installed tn office on aug. 7 1914. apart from fiscal and dip- lomatic problems inherited from his predecessors, he had to face new difliculties created by the outbreak of the world war. the neutrality of the republic was proclaimed, and to ensure its ob- servance suarez, the foreign minister, addressed a circular letter to the newspaper editors throughout the country on nov. 27, exhorting them to be strictly neutral in their comments on events. colombia passed through the war period without any diplomatic difficulties arising. the panama setilement.—in feb. 1918 marco fidel suarez was elected president, and took office on aug. 7. on nov. 3 1919 congress authorised colombia’s adhesion to the league of nations, but served notice that her acceptance of article 10 of the covenant did not imply her acknowledgment of panama as an independent nation. two delegates attended the assembly of the league at geneva in 1920. the old trouble arising from the secession of panama again absorbed attention, and the terms ot its settlement excited political fecling. the thompson-urrutia treaty, as originally drafted, had been ratified by the colombian congress, but the u.s. senate proposed several drastic modi- fications. one of these involved a pledge on the part of colombia of her recognition of the independence of panama. the privi- leges allowed to colombia in the use of the panama canal were also somewhat reduced. the treaty stipulated that panama should accept as her southern boundary the line sketched in a colombian law of 1855. of the indemnity of $25,000,000 for the loss of panama it was further provided that $5,000,000 should be paid within six months of the treaty coming into force, and the balance in four annual instalments. because of the factious opposition in the colombian congress to these modifications, president suarez resigned his position on nov. 11 1921 and was succeeded by gen. jorge holguin. on dec. 22 1921 the colombian congress ratified the modified thompson- urrutia treaty, which had been adopted by the u.s. senate in april, and two days later it was approved by president holguin. on feb. 12 1922 gen. pedro nel ospina, candidate of the con- servative party, was elected president, and was installed on aug. 7 1922. questions of financial reform came under review early in the regime of gen. ospina, and at the invitation of the government a commission, headed by prof. kemmerer of princeton uni- versity, arrived in colombia in march 1923, to undertake the task of introducing greater financial efficiency and establishing an effective gold standard. in may 1924, at the instance of the united states govt., the envoys of colombia and panama in washington signed an agreement which provided that each government should designate a minister to the other contracting party and thus formally establish normal diplomatic relations colombia between the two states. on aug. 1 1924 nicold4s victoria, the minister of panama, was received at bogota, and colombia’s representative to panama was duly accredited. a mixed com- mission was appointed to survey the boundary between the two countries. in feb. 1926 dr. miguel abadia mendez, chancellor in the cabinet of gen. ospina, was elected president for the term 1926-30. ; constitutional changes——in the period 1910-25 important modifications of the constitution of 1886 were made. a law of june 6 1910, provided that in case of vacancy in the presidency, two persons sclected by congress were temporarily to exercise the powers of the president in a designated order. it was also provided that no person could be re-clected for a second term as president. on oct. 31 1910 another law made important con- stitutional amendments, among which was a provision that only male citizens who were able to read and write and either owned real estate or had an income, should be allowed to vote in con- gressional and presidental elections. the method of constituting the senate was also altered by providing that its members should be chosen by the assemblies in the different departments into which the country is divided. the supreme court was empowered to determine whether or not a law should be enforced if the national government, or a citizen, denounced it as unconstitu- tional: in the exercise of this power certain concessions, originally granted to colombians and then transferred to foreign corpora- tions, were held to have been unconstitutionally granted, and as the terms had not been fulfilled, were cancelled. during the administration of president concha, congress enacted a law providing for the re-establishment of the council of state, which was to act as an advisory body to the president. defence.—in 1925 colombia had a defence force with a peace establishment of about 5,coo. the system of compulsory military training was nominally in force, the conscripts undergoing six months training. actually exemption from service is freely granted. in 1924 arrangements were made with the swiss govt. to send out a military mission of five officers, besides aviators, to introduce the swiss system of training and organisation. the infantry is armed with the mauser nfle and the artillery has schneider-creuzot gugis. expenditure on defence amounted tn 1924 to $2,648,300. | education.—there are primary, secondary, professional, in- dustrial and art schools in colombia, as well as the university of bogot4 (founded in 1572) and the four provincial universilics of cartagena, pop$y4n, medellin and pasto. education ts under the control of the ministry of public instruction, but the church has wide powers, and so far as direction and supervision go, dominates the entire scholastic system. the industrial and art schools are mostly directed by the religious orders. primary education is free. in 1924 a german commission of three mem- bers began to advise the colombian govt. on educational mat- ters, and aided by a council of three colombians, headed by dr. tomas vargas, took in hand the modernisation of the system. in 1924 there were in colombia 6,674 primary schools having on the average only one teacher each. the attendance at these schools was 417,054. the vote for public instruction in 1923 was $1,108,190, and in 1924 the actual expenditure under the heading of ‘‘ instruction and public health ” was $2,234,672. in addition departments and municipalitics spend moncy on education. ii. economic history staple products —the principal industry of colombia is the production of mild coffee, in which the expansion has been remarkable, the value of exports rising from $18,369,768 in 1913 to $53,630,661 in 1924, dropping through crop shortages to $42,968,544 in 1925. the country is the sccond largest world producer of bananas. cattle breeding has also been developed as the result of the clearing of forests and the sowing of imported grasses. in ro2r there were estimated to be 8,000,000 head of cattle, a figure which increased to 9,000,000 in 1925. the carry- ing capacity of the cattle lands is estimated to be 50,000,000 head. cocoa, sugar, tobacco, balata, pita fibre, ivory nuts, sisal-hemp, silk, tropical fruits, wheat and maize and cotton are the staples pomp ig of agricultural produce. in 1925 arrangements were made for a british expert commission to visit the country and report on the development of the cotton industry, which is increasing in im- portance. the mission arrived in colombia on feb. 27 1926. medicinal plants such as cinchona, ipecacuanha, sarsaparilla, etc., are also grown. the forests are valuable chiefly for the pro- duction of cedar and dyewoods. rubber grows in most of the departments. on the coasts there are valuable pearl fisheries. the republic is famous for emeralds and platinum. other mineral products of importance are gold, silver, copper and iron, while a small amount of coal is produced. asphalt is also being worked and there are large salt deposits under state control. of recent years the country has been vigorously prospected for oil, and rich fields have been tapped by british and american com- panies. colombia has been classified by the u. s. geological survey as the largest potential oilfield in the world. the tropical oil company has a big concession in the department of santan- der, and at the end of 1925 was producing 20,c00 bbl. a day. to convey the oil from the santander fields to the point of shipment the andean national corporation, under a contract with the government, laid down a national pipe-line, the first section of which (240 m.) was under construction at the end of 1925. encouraged by high protective tariffs, manufacturing indus- tries progressed considerably after the war. the development of cotton growing, sheep raising and silk production assisted the growth of the textile industry, and factories were erected at barranquilla, medellin, bogote and cartagena. the manufac- ture of panama hats, and the export of the finished product, greatly increased in the post-war pcriod. the country’s indus- trial development, however, is still greatly retarded by inace- quate means of transport. foreign trade-—colombia’s foreign trade, which had previ- ously shown only a slight annual increase in volume, was seriously checked during the world war. since then, however, it has greatly increased. imports e-xports imports exports gh $ $ s 1913 | 28,535,779| 34,315,251 | 1921 | 33,078,317 | 63,042,132 hom |) l77bho,o1g)| 31,579,131 | 1922 | daetats,024 | 53,516,331 1918 | 21,783,002 | 37,443,991 | 1923 | 57,783,798 | 60,257,172 1919 | 47,451,724] 79,010,983 | 1924 | 52,347,914 | 70,615,819 1920 | 101,397,906 | 71,017,729 | 1925 | 57,783,796 | 60,115,435 with the exception of 1920, when there was a “ boom ”" in im- ports to replenish stocks depleted during the war, a favourable balance of trade was maintained. ‘fhe main item of exports was coffee, the volume and value of which rose from approximately 450,000 bags, worth $18,369,768 in 1910, to 2,500,000 bags, worth $42,968,544 in 1925. other important exports were ba- nanas, platinum, hides, tobacco, cattle and panama hats. the export trade was largely to the united states, great britain, holland, mexico, germany and belgium. imports mainly com- prise railway material, locomotives and rolling stock; engincer- ing, road-building and general construction materials; agri- cultural and other machinery; commercial vehicles, hardware, jute bags, cutlery, crockery, wines and spirits, drugs and chemi- cals and provisions. in 1925 the chief countries from which imports were received were the united states, great britain, germany, italy, france, spain and holland. national finances —there was a great improvement in the national finances in the period t910-25, and particularly in the two years immediately following the adoption of fiscal and other reforms recommended by the kemmerer financial mission, this body spent six months in 1923 in investigating the entire system of national accountancy, revenue and expenditure, banking and the monetary system. drastic reforms followed, the results of which are admitted to have placed colombia among the most healthy and stable of latin american countries so far as public finance is concerned. a proper valuation of the national assets was made and a system of independent audit of accounts intro- duced. in the same period the payment of the instalments of the indemnity for the loss of panama helped to strengthen the 678 financial position of the republic. the first instalment of $5,000,- ooo was paid on dec. 7 1922 and was used the following year to establish the central bank as recommended by the kemmerer mission. three subsequent payments were made before the end of 1925, and there was a gain to the republic on exchange. in 1910 the revenue of colombia totalled $10,827,560, and the expenditure was $11,501,442. in 1924 the ordinary revenue amounted to $33,458,053, to which was added extraordinary revenue (mainly the instalment of the american indemnity ) of $6,391,982. ordinary expenditure (national services) amount- ed to $32,024,244, while that on extraordinary account was a further $6,899,693. on both accounts the year closed with a surplus of $926,097. the year 1925 closed with total receipts of over $40,000,000, not including the quota of the indemnity, and the biggest surplus that had been known in the history of the country was realised. on dec. 31 to10 the public debt was $17,495,127, consisting of external obligations of $14,839,000, and internal debts of $2,656,127. at the end of 1924 the gross debt was $36,716,827, the external debt being $19,293,862 and the internal $17,422,965. during 1924 the gross indebtedness was reduced by $6,040,984. colombia’s credit stands very high abroad owing to the regular fulfilment of the debt services and the steady amortisation of the joans. the main operations after 1910 were the loan of £1,500,000 at 6% obtained in london in 1913, and that of $5,000,000 (u.s.) raised in the united states in oct. 1922, with interest at 64%, these and other loans carrying a sinking fund of 1%. long credits have been obtained for the purchase of railway and other material. owing to the reorganisation of the finances and admin- istration, and also to the influx of money in the form of the panama indemnity, no further effort was made by the central govt. to float foreign loans. money and banking—the monetary unit is the gold peso ($) worth $0.975 united states currency, and four shillings english. the five peso gold piece has the same weight and fineness as the english pound, which is also legal tender in colombia. the peso is divided into 100 cents. the currency consists of nickel coinage of 1,2 and 5 cents;silver for ro, 20 and 50 cents; notes for 50 cents, i, 2, § and 10 pesos, and gold coins for $2.50 and $5. before 1910 the paper peso had dropped to a value of one cent, and all foreign coinage was allowed to circulate. the government of the day exchanged one gold peso for every 100 paper pesos. from 1gro the money in circulation was restricted toa total of about $10,000,000. ; the whole question of the currency system was reviewed by the kemmerer mission. among the proposals adopted in 1923 were those for a new banking system embodying the creation of a central national bank, and the reformation of the currency. while the mission was at work the collapse of one of the biggest of the local banks threatened to precipitate a commercial crisis. the banco de la republica was hastily established, with the sole right to issue notes based on a minimum gold reserve of 60%, supplemented by short-dated commercial paper. at the same time arrangements were made to reduce the circulation of old notes issued by other banks. in the first year of its existence the banco de la republica stabilised the currency on an effective gold basis, reduced the discount rate, increased the gold reserve against the legal requirement, and generally restored complete confidence. against the total note issue of $33,555,890 in cir- culation on june 30 1925, there was a gold reserve of $26,286,703. all local and foreign banks in colombia are under the control of the law through a state banking superintendent. during 1925 an agricultural mortgage bank was established to afford credits for the agricultural development of the country. communications—the main approach to colombia from europe and the united states is, on the atlantic side, through the port of cartagena, and on the pacific, through buenaventura. vessels of the united fruit company call at cartagena, puerto colombia and santa marta. the harrison, leyland and horn lines maintain services from europe, and other companies, using the panama canal, serve the pacific ports. colombia can also be reached through venezuela, via lake maracaibo. inland traffic colombo—colorado from the atlantic to the capital of bogot& mainly follows the magdalena river, which is navigable for some hundreds of miles. short railways exist in various parts of the republic and the policy of the government is to link them up and form three grand trunk systems, one connecting the capital with the magdalena, the second from cartagena through the cauca valley southward to the frontier of ecuador, and the third eastward from buena- ventura to bogota. colombia’s railway policy is to construct, own and operate her own lines. the director general of railways re- ported at the end of 1925 that the state operated 517 m. of line and had under construction, or had planned, a further 370 miles. colombia devoted most of the panama indemnity to public works, including the construction or purchase of railways. a vigorous programme of road building was also adopted in 1925. the republic possesses the longest aerial ropeway in the world, and in 1925 the construction was begun of a ropeway for passengers and goods from gamara on the magdalena to cficuta, a distance of 105 miles. aviation services have proved very successful, especially for shortening the time of travel between cartagena and other atlantic ports and bogota. aerial services are operated over a distance of 1,000 miles. telegraph lines exceed 15,000 m. in length, and there is wireless communication with the united states and europe. cable communication is maintained via colon with the united states, and direct with europe. brbliography.—p. j. eder, colombia (1913); v. levine, colombia (1914); p. l. bell, colombia, a commercial and industrial handbook (1921); w. s. robertson, ihistory of the latin-american nations (1922); and hispanic-american relations with the united states (1923); b. niles, colombia, land of miracles (1924); a. martinez, colombia year book 1925-26 (1926) see also annual reports of the corporation of foreign bondholders (1910, etc.}; pan-american union, colombia, general descriptive data (1910, etc.); informe del afinistro de relaciones exteriores al congreso (1910- , etc.); in- forme del ministro de instruccion publica al congreso nacional (1911-, etc.); republica de colombia, leyes expedididas por el congreso nacional en su legislaiure (1911-, etc.); informe del ministro de tiacienda al congreso (1914, etc.); afemorta del ministro del tesoro al congreso de 1923, 2 vol. (1923); u. s. dept. of commerce: trade information bulletin no. 223. colombia, commerce and industries, 1922 and 1923 (1924); brit. dept. of overseas vrade: reports on the commercial and economic situation in the republic of colomhia (1922, 1924, 1925); colombian trade review (monthly). (w. s. ro.; l. ma.) colombo, ceylon (see 6.713), had, in 1921, a population of 244,163, which includes parsees, tamils, malays and a number of people of mixed portuguese and dutch descent. in rg2i the birth rate, 25-8 per 1,000, was the highest for 14 years. the death-rate was 25:2 per 1,000. an ambitious drainage scheme for an area of 10 sq. m., taken in hand by the municipality, was modified for financial reasons, and the reduced scheme, with main works at madampitiya, was brought into use in 1921. in that year a university college was founded, and the college building and laboratories were erected in 1922. the harbour, with a water area of about 600 ac., has fine accommodation for large vessels since the extension of the southwest breakwater in 1911. a dredger is regularly at work in the harbour. communication has been established between colombo lake and the harbour, and a railway built to connect with the main line. oil depots have been established at blomendhal and kolonnawa.