714 



THE STANDARD DICTIONARY OF FACTS 



an engine is said to be of 100 horse power (h. p.) 

 when it has a lifting capacity equivalent to 

 3,300,000 pounds one foot high per minute. To 

 ascertain the horse power of an engine multiply 

 together the pressure in pounds on a square inch 

 of the piston, the area of the piston in inches, 

 the length of the stroke in feet, and the number 

 of strokes per minute, divide the result by 33,000 

 and the quotient, less one-tenth, allowed for loss 

 by friction, will give the horse power. Engines 

 are frequently said to be of so many horse power 

 nominal ; the real or indicated horse power, how- 

 ever, often exceeds the nominal by as much as 

 three to one. 



Illiteracy. The following percentages in- 

 dicate the relative illiteracy of the chief nations 

 of the world. In Rumania, 88.4 per cent, of the 

 population can neither read nor write ; in Servia, 

 79.3 per ce/it.; in Portugal, 79.2; in Spain, 68.1 

 per cent. ; in Russia, 61.7 per cent. ; in Hungary, 

 47.8 per cent.; in Austria, 35.6 per cent.; in 

 Italy. 32.9 per cent.; in Greece, 30 per cent.; in 

 Belgium, 10 per cent.; in Ireland, 7.9 per cent.; 

 in France, 4.7 per cent. ; in England, 3 per cent. ; 

 in Scotland, 2.5 per cent. ; in The Netherlands, 

 2.3 per cent.; in Finland, .5 per cent.; in Den- 

 mark, .2 per cent. ; in Switzerland, .13 per cent. ; 

 in Sweden and Norway, .08 per cent.; in The 

 German Empire, .05 per cent.; and in Saxony, 

 Bavaria, Wurttemberg and some other German 

 states only rarely a person can be found who 

 cannot read and write. In the United States 

 the ratio of illiteracy among the whites is 6.2 

 per cent. 



Libraries. Libraries existed in ancient 

 Egypt and Assyria, and Pisistratus is credited 

 with the honor of introducing a public library 

 at Athens about B. C. 337. Cicero and various 

 wealthy Romans made collections of books, and 

 several Roman Emperors established libraries, 

 partly with books obtained as spoils of war. 

 By far the most celebrated library of antiquity 

 was the Alexandrian. In the West libraries of 

 any note were founded in the second half of the 

 Eighth Century by the encouragement of Charle- 

 magne. In France one of the most celebrated 

 was that in the Abbey of St. Germain des Pres, 

 near Paris. In Germany the libraries of Fulda, 

 Corvey, and in the Eleventh Century that of Hir- 

 schau, were valuable. In Spain, in the Twelfth. 

 Century, the Moors had seventy public libraries, 

 of which that of Cordova contained 250,000 

 volumes. In Britain and Italy libraries were 

 also founded with great zeal, particularly in the 

 former country, by Richard Aungerville; in the 

 latter by Petrarch, Boccaccio, and others. After 

 the invention of the art of printing this was done 

 more easily and at less expense. The principal 

 libraries of modern times are : 



LIBRARY CITY No. OF VOLS. 



Bibliotheque nationals, . . Paris 2,602,000 



British Museum London 2,003,000 



Library of Congress, . . . Washington, . . 1,434,000 



Imper. publicnaja biblioteka.St. Petersburg, . 1,329.000 



Konigliche bibliothek, . . . Berlin 1,200,000 



Kon. Hof- u. Staatsbiblio- 



thek Munich 1,000,000 



K. u. k. Hofbibliothek, . . Vienna 900,000 



Universitats- u. landesbib- 



liothek Strasburg, . . . 814,000 



Public Library Boston 812,260 



Publicnyj i Rumjancovskij 



musej Moscow, .... 800,000 



LIBRARY CITY No. OF VOLS. 



Public Library Astor, 

 Lenox, and Tilden Foun- 

 dation New York City, . 787,700 



Biblioteca nacional, .... Madrid 000,000 



Bodleian Library Oxford 600,000 



K. k. Universitats-biblio- 



thek Vienna 596,526 



Harvard University Library, Cambridge (U. S.) 575,889 



Cambridge University Li- 

 brary . . . . Cambridge (Eng.) 550,000 



Det store kongelige biblio- 



thek Copengahen, . . ">:.(). 000 



Universitats-bibliothok, . . (iiittiiiKfii, ... 



Universiteit bibliotheek . . Amsterdam, . . 500,000 



Kon bibliotheek The Hague, . . . 500,000 



Other large and valuable libraries arc: tho 

 royal libraries at Stuttgart and Dresden; the 

 university libraries of Genoa, Prague, Gottingen, 

 Upsal, and Dublin; also the libraries of Venice. 

 Florence, Milan, Bologna, Naples, and the Ad- 

 vocates', Edinburgh. The Vatican library, 

 Rome, and the Bodleian, Oxford, are particularly 

 valuable in rare books and manuscripts. Tho 

 spread of education, and the consequent grow- 

 ing taste for knowledge, has called into existence 

 innumerable smaller libraries, ready of access, 

 and providing such literature as the special class 

 of readers demand. This public library system 

 has naturally been most developed in highly- 

 educated countries such as Germany, France, 

 Great Britain, and the United States. 



Light. That peculiar property of matter 

 which affects the nerves of sight, and causes us 

 to see. A ray of light is an exceedingly small 

 portion of light as it comes from a luminous 

 body. A beam of light is a collection of parallel 

 rays. A medium is a body which affords a pas- 

 sage for the rays of light. A pencil of rays is a 

 mass of diverging or converging rays. Converg- 

 ing rays are those which tend to a common point ; 

 diverging rays, those which come from one point, 

 and continually separate as they proceed. The 

 rays of light are parallel, where the lines which 

 they describe are so. The radiant point is tho. 

 point from which diverging rays proceed. Tho 

 focus is the point to which the converging rays 

 are directed. Light passes off from a luminous 

 body in all directions ; and its intensity decreases 

 as the square of the distance increases: thus, if 

 one object is twice as far from a luminous body 

 as another of the same size, it will receive only 

 one-fourth as much light as the latter. The 

 velocity with which light travels is enormous; 

 it was estimated, on astronomical data, at Is.!, 

 470 miles per second; but according to L6on 

 Foucault's recent experiments with the "turning 

 mirror," it is 18,5,170 English miles per second; 

 and it requires little more than a quarter of an 

 hour to pass through the diameter of the earth's 

 orbit. When light encounters an obstacle, some 

 of it is reflected, some absorbed, and, if the inter- 

 posed body is not opaque, some of it is trans- 

 mitted. During transmission it is modified. 

 being in some cases, as with doubly refracting 

 crystals, decomposed into two white rays, pos- 

 sessing different properties; and in others, as 

 with glass prisms, decomposed into a number 

 of colored rays, accompanied by rays which an- 

 colorless, and in fact invisible, but which have 

 marked chemical and calorific properties. When 

 luminous rays pass into a dark chamber through 

 a small aperture, and are received upon a screen, 

 they form images of external objects. These 



