VALENCIA. 796 VALENCY. VALENCIA. The capital of the State of Caral)olio. Venezuela, situated 24 miles south of Puerto Cabello, with which it has railway con- nection, near the western end of Lake Va'lencia or Tacarigua (Map: Venezuela, D 2). Valencia is the second city of the Republic, and is well constructed with broad streets, well-kept plazas, a beautiful market and alameda. Valencia con- tains a notable cathedral erected during the first half of the nineteenth century. The city is on the banks of the Aragua River. The chief e.xports are coffee, sugar, cacao, and hides. Popu- lation, in 1894. 38.054. Valencia was founded in 1555. During the struggle for independence it was the scene of battles fought by Bolivar in 1814 and 1821, the latter of which gained the freedom of Venezuela from Spain. On accoinit of the various sieges from 1810 to 1821 and the great earthquake of 1812, there are many ruins in the vicinity. VALENCIA, rNivERSiTT OF. A Spanish university, founded by the union of an episcopal foundation for theology and a municipal school of arts, medicine, and civil and canon law. both dating from the middle of the fourteenth century. These were combined about 1500. Several col- leges were founded in the sixteenth century, the period of the greatest prosperity of the institu- tion. From that century it sank in numbers and reputation. It was reorganized in the decade 1848-58, and has since grown to be oite of the leading iiniversities in the kingdom. It has the three' faculties of law, i)hysics-chemistry, and medicine, and in 1901 had 1728 students." VALENCIENNES, va'UiN'syen'. The capital of an arrondissement in the Department of Nord, France, and a fortress of the second class, at the junction of the Rhondelle and the Scheldt, 30 miles by rail southeast of Lille (Jlap: France, K 1). Broad boulevards are laid out on the site of the old fortifications, which were demolished in 1892. There are many houses of the seven- teenth century, which give the streets a mediaeval apearance. The handsome Hotel de Ville, pure seventeenth century except the facade, contains a large collection of paintings, especially of the Flemish school (including splendid specimens of Rubens), and a collection of sculptures. The Gothic Church of Saint G#ry. dating from the thirteenth century, with a modern tower, and the Church of Notre Dame du Saint Cordon, a modern structure in thirteenth-century .style, with beautiful stained-glass windows by Lfvi'que. are worthy of notice. In the old Jesuit College is the municipal library of more than 25.000 vol- umes, containing much valuable Romance litera- ture. There are an academy for sculpture and painting, a museum of natural history, an im- mense hospital, a lycfe and an arsenal. The famous Valenciennes lace is no longer manufac- tured. The extensive coal-fields amid which Valenciennes lies have made it a metallurgical centre. Glass, sugar ( from beets ) , chemicals, carnbrics, and lawns are also manufactured. Chicory cofl'ee is shipped in large (juantities. Population, in 1901, 30,940. Valenciennes is the Roman Valentiana. It came to France by fhe Treaty of Nimeguen in 1678. VALENCIENNES, Achille (1794-1865). A French zoologist, born in Paris and. educated there. In 1836 he became professor of ichthy- ology at the Museum of Natural History. He shared in Cuvier's Histoirc iiatiirrllc ik's pois- sons, which he continued (22 vols., 1829-49). 'alenciennes wrote Uistoire natureUc drs mol- li(s(jiies. dcs unnclides et des zoophytes ( 1833) . VALENCY (Lat. valciitia. strength, from vdlcr, to be strong, able; connected with Olr fhnth, power, Lith. galeti, to be able, Goth. wuldan, OHG. ivaltan, Ger. walten, AS. ireuldan Eng. imeld), Valence, or Atomicity. In chem- istry, the combining capacity of an atom, with reterence to the number of other atoms with whuli It can be directly combined. The concep- tion of valency is an offspring of the atomic and molecular theories. These theories led to a knowl- edge of the numbers of difl^erent atoms making up the molecules of compounds; but as in many cases very different compounds were found to have the same composition and the same molec- ular weight, it became clear that ditterences in the chemical and physical properties of com- pounds must often be caused bv differences in the manner of combination of their atoms. Those^ differences of combination had to lie investigated and thus arose the question. In what manner does affinity act in holding together the atoms of compounds? In considering various com- pounds with a view to obtaining some light on this question, chemists were gradually led to a series of assumptions, the incorporation of which in atomic chemistry has proved exceedingly fruit- ful. First of all it was observed that, in compounds, of hydrogen with some one other element, one atom of hydrogen can hold in combination only- one atom of the other element ; this was shown by such compounds as hydrochloric acid (HCl), hydrobromic acid (HBr). hydriodic acid (HI)' etc., and the fact was expressed by saving that hydrogen is toiii-nleiit or mniiad. The val- encies of certain other elements were then found by considering their compounds with hydrogen, on the principle that by every unit of their combining capacities the atoms of those elements can hold one atom of livdro"en- for hydrogen it.self is univalent, i.e. h.s unit com- bining capacity. From the compounds alreadv mentioned it may be seen that the atoms of chlorine, bromine, and iodine are, like hydrogen, univalent; for each atom of these elements "can be combined with only one atom of hydrogen. Similarly, compounds like water (H..6). sul- phureted hydrogen (SH„), anmionia" (NH3) and marsh-gas (CH,) show that oxygen and! sulphur are divalent, that nitrogen is tri-valent, and that carbon is quadri-valent. The valencies peculiar to some of the elements being thus- established by an inspection of their compounds with hydrogen, the valencies of the other ele- ments can be found by studying their com- pounds not necessarily with hydrogen, but with any element of known valency.' Thus compounds like sodium cliloride (Na CI ) ,'postassiuin chloride (KCI). etc., show that the atoms of sodium and potassium are univalent; for they can hold in combination only one atom of another univalent element. The same thing is shown by the fact that sodium or potassium takes the place of one atom of hydrogen in acids ; for example, in hydro- chloric acid:
