CHROMATIC SCALE 



1371 



CHRONOLOGY 



During the Spanish-American War he went to 

 Cuba with the "Rough Riders," and the illus- 

 trations he made there, which were published 

 in Scribner's and Harper's magazines and in 

 Collier's Weekly, aroused the first interest in 

 his work. A portrait of Colonel Roosevelt 

 gained him special prominence later, but he 

 is best known through his black and white 

 illustrations of serial stories in magazines and 

 for his illustration of several of James Whit- 

 comb Riley's books. Christy pictures are 

 favorites, also, as colored prints on magazine 

 covers. 



CHROMATIC, kro mat 'ik, SCALE, in music, 

 the scale produced by dividing the whole tones 

 of the natural, or diatonic, scale into half-tones. 

 The chromatic half-tone, or semitone, is the 

 interval between a note and that note raised 



i 





CHROMATIC SCALE 



by a sharp or lowered by a flat. The chromatic 

 scale, with the two half-tones already in the 

 diatonic scale, is an octave divided into twelve 

 semitones. Composers make use of the chro- 

 matic tones to produce many beautiful effects 

 in music. See Music; SCALE. 



CHROME, krome, a name applied to a num- 

 ber of substances used as the basis of paints. 

 Chrome yellow is a compound of chromic 

 -acid and lead. Chrome green, a compound of 

 chromium and oxygen, is used by calico print- 

 ers and for enamels; it is also the basis of a 

 number of green paints and dyes, which are not 

 poisonous. Chrome red is a compound of 

 chromium and lead. All chrome colors are 

 noted for their clearness and brilliancy. 



CHROMITE, kro' mite, or CHROMIC IRON 

 ORE, a mineral, the chief ore from which 

 chromium is extracted. It contains about 

 sixty-eight per cent of chromic oxide and about 

 thirty-two per cent of ferrous oxide. It is of 

 black or brownish-black color, with a sub- 

 metallic luster, and resembles magnetite or 

 magnetic iron ore in appearance. Chromite 

 is largely used in the preparation of paints, 

 in calico-printing 'or dyeing of cotton goods, 

 and in the extraction of chromium and its 

 compounds. Formerly it used to be mined in 

 great quantities in the United States, but at 

 present only small quantities are produced 

 from that source. The chief sources of supply 

 are Canada, New Zealand, Australia, Russia and 

 Turkey. The chemical formula of chromite is 

 FeCiiO 4 . (See CHROMIUM). 



CHROMIUM, kro'mium, a rare metal, valu- 

 able chiefly for its compounds. It is never 

 found in a free state, but may be obtained 

 from chromite, a compound of chromium and 

 iron, sometimes known as chromic iron ore (see 

 CHROMITE). Chromium is a hard, steel-gray 

 metal which is usually produced in the form of 

 a powder. It melts only at a very high temper- 

 ature, and for this reason is but little used. 

 A small quantity, less than one per cent, added 

 to steel, produces chromium steel, noted for 

 its hardness, fine texture and strength. A 

 compound of chromium and lead forms chrome 

 yellow, which is an important basis of yellow 

 paint. Chrome green, or ultramarine green, is a 

 compound of chromium and oxygen. Potas- 

 sium bichromate, a compound of chromium 

 and potassium, is used in dyeing, in photog- 

 raphy and in the production of a number of 

 chromium compounds used in the manufacture 

 of paints. Chromite is also an important 

 source of paints. 



CHRONICLES, kron'ik'lz, BOOKS OF, two 

 books of the Old Testament which follow the 

 books of Kings. The name in Hebrew means 

 Acts of the Days. In the Hebrew scriptures 

 Chronicles consists of only one book. The 

 division was made when the Septuagint (which 

 see) was written. Chronicles differ from Kings 

 in giving more fully the religious side of the 

 history of Israel during the period covered, 

 and in giving the history of the kingdom of 

 Judah to the exclusion of that of Israel after 

 the kingdoms were divided. It is thought that 

 these books were written by the priests. See 

 KINGS, BOOKS OF. 



CHRONOLOGY, kronol'oji, the science of 

 dividing time into periods and of giving to 

 historic events their proper dates. The unit 

 of time in chronology is the year. When the 

 date of an event is given, we mean that such 

 an event happened so many years after or 

 before some great point in history, which is 

 regarded as the beginning of an era. 



We say that Columbus discovered America 

 in A. D. 1492, meaning that he made his great 

 discovery 1,492 years after the birth of Christ; 

 A. D. is the abbreviation for the Latin expres- 

 sion Anno domini, meaning in the year oj our 

 Lord, and the birth of Christ is the beginning 

 of the Christian Era. Dates of events occur- 

 ring before the birth of Christ were written 

 with the letters B. c.; as, Julius Caesar invaded 

 Britain in 55 B.C. This system of fixing dates 

 is the one now commonly employed through- 

 out the enlightened parts of the world. 



