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* CHELSEA VILLAGE. 559 CHEMISTRY. the city, was persuaded to sell it in building- lots. The iiiinie is still in use by old residents, and is preserved in Chelsea Square, between Twentieth and Twenty-first streets, and Ninth and Tenth avenues, the site of the (Jeneral Theo- logical Seminary. CHELTENHAM, ehel'fn-ani (village on the Clielt I. A ijiuui<i])al and Parliamentary bor- ough and fashionable watering-place in Glouces- tershire, England, eight miles northeast of the city of Gloucester (Map: Kngland, E 5). It lies in a picturesque valley, on the Chclt, a small stream which rises in the adjacent hills and flows into the Severn. It is sheltered on the east and southeast by a semicircle of the Cotswold Hills. The town is regularly laid out and well built, and has fine public promenades, gardens, ter- races, and squares. Among its numerous churches, the Parish Church of Saint JIary's, dat- ing from the Fourteenth Century, is a fine example of Gothic architecture. The town was incorporated in 1870. It returns one member to Parliament. The town authorities have shown a desire to give it all modern improvements by installing electric lighting, providing an excel- lent water-supply and a modern system of sewerage in connection with three large sewage farms. They also maintain a public library, an art school, baths, a cattle market, and slaughter- houses. Cheltenham has become famous for its colleges and schools, among which are the grammar school (founded in 1574), Clieltenham College, training colleges for school-teachers, and many private schools. Its popularity, how- ever, is chiefly due to its mineral springs, con- sidered to be specially efficacious in cases of dyspepsia and affections of the liver. In conse- quence, such a large proportion of the resident population consists of Anglo-Indians that the town has been nicknamed 'Asia Minor.' The Cotswold Hunt holds its meets here, and draws many visitors during the hunting season. Ro- man remains have been discovered on the site of the town. It is mentioned in Domesday Book, but it was not until the discovery of its mineral springs, in 1716, that it began to rise into im- portance. The visit of George III. in 1788 set upon it the seal of fashion. Its gro^-th in popu- lation in the Nineteenth Centui-y was very rapid. In 1804 it numbered onlv .3000; in 1841 it had increased to 31.000; in 1801 it was 47,121: and 1901, 49,430. CHEMICAL FIRE - ENGINE. See Fire- Engixe. CHEMICAL NOTATION. See Chemistry, Ckeni iral Form iilas. CHEMISTRY. The science of the various material substances that are capable of exist- ence, of their relations to one another, and of the laws governing their various transforma- tions. The Xame. The origin of the word chemistry is uncertain. Chemia (or Chemi) is the old name of Egypt, and as the art of making gold and silver was first practiced in that country, the ficience of chemeia ( x'//"'" ) niay have meant originally 'the science of Egypt.' Later, how- ever, at the time of the Alexandrian alchemists, the word was used to denote some substance; and as. on the one hand, the word chemi means 'black,' and. on the other hand, the first step in the tran«nnilation of metals is known to have been a process of blackening, we conclude that chemeia may at that time have denoted the 'philosopher's stone' — i.e. the substance em- ployed in the process of blackening the metals. Similarly, in the form al-kimiija, the term is used also by the e;irly Arabic writers to denote, not their art, but a substance employed in that r.rt. With them, however, the term was used iu much the same sense as the word al-iksir, and this suggests another possible derivation. The word ikslr is derived from the Greek xtruii (f;/p(if), which means dr;/. Possibly, then, the word klmii/u may have been derived from the Greek chi/mos (xi'/i4f)i which means liquid; and while at one time both iksir and khnitja, were used to denote a substance, the words chymeia x^/icia) and alchymy gradually came to denote the art in which that substance was employed, the sub- stance itself (the philosopher's stone) retain- ing only the name al-ikstr. TuE Br. ciies of Chemistry. The facts of chemistry have been grouped in a variety of ways, either in the interests of research or ac- cording to their usefulness in connection with kindred sciences or with the arts. Hence such titles as Animal, Vegetable, Medical, Astronom- ical, Metallurgical Chemistry, etc., which in a general way explain themselves. Chemistry proper may be considered as comprising the fol- lowing four branches: analjiiieal, descriptive, general, and applied. Analytical chemistry may be defined as the art of determining the compo- sition of substances; imder the names of tech- nical analysis, physiological analysis, etc., many of its methods form an important part of ap- plied chemistry. Descriptive chemistry deals with the chemical and physical characteristics of substances ; it forms a record of the properties of substances, which are arranged, for conve- nience of reference or for didactic purposes, in accordance with the principles of general chem- istry. The two great subdivisions of descriptive chemistry are inorganic and organic chemistry, the latter dealing with the compounds of car- bon, the former with those of all the other elements. General chemistry includes theoreti- cal and physical chemistry, which are usually treated together: theoretical chemistry com- prises the laws of the composition and chem- ical behavior of compounds ; physical chemistry treats of the physical properties of compounds, of homogeneous mixtures, and of the physical phenomena (thermal, electrical, etc.) accom- panying the transformations of substances in general. Applied chemistry comprises all the facts and methods of chemistry that find prac- tical emplo.vment. The most important sub- divisions of this branch are: (1) Biological chemistry, including the chemical facts connect- ed with physiological and pathological phenom- ena in animals and plants; (2) agricultural chemistry, which deals with problems of rural economy; and (3) industrial, technological, or practical chemistry, which deals with the uses of chemistry in the arts and manufactures. The Methods of Chemicvl PuiLosopnY. Like any other science, chemistry may use two dif- ferent ways in discovering and demonstrating its general principles. On the one hand — and this is the surest way — a principle may be in- duced from a large number of experimental observations; it is then nothing but the state- ment of a general fact, and is termed an em-