368 ACROPHYSICS. 



The first collection of chemical facts, freed from the mysticism of 

 Alchemy, was published by Earner, in 1670 : but the phlogistic 

 theory, suggested by Beccher in 1669, and more fully developed by 

 Stahl', first gave these facts a connected and scientific form. This 

 theory supposed the metals, and other combustibles, to be compounds, 

 containing phlogiston, or the substance of heat, which they gave out 

 in burning. Chemistry was thenceforward rapidly advanced, by the 

 labors of Boerhaave, Bergmann, Scheele, and others. In 1754, the 

 discovery of carbonic acid gas, by Dr. Black, led to the discovery 

 of other gases, and originated what is called Pneumatic Chemistry ; 

 forming an important era in this science. In 1778, Lavoisier pro- 

 posed his antiphlogistic theory ; that bodies when burning, instead 

 of emitting any substance, absorb and combine with oxygen : a 

 theory which was soon adopted by Bertholet, and proved by exact 

 experiments. 



The chemical nomenclature now in use, originated with Guyton 

 de Morveau, about 1780 ; and was soon generally adopted. The 

 idea that chemical compounds are formed of elements uniting in de- 

 finite proportions, originated with Wenzel, of Saxony, in 1777, but 

 was fully developed and generalized in 1803, by Dalton ; whose 

 laws of combination, proved by the labors of Wollaston, Davy, 

 Gay Lussac, Thenard, Vauquelin, Berzelius, and others, are now 

 regarded as the basis of this great science. The atomic theory, 

 already referred to, (p. 343,) as known to the ancients, and main- 

 tained by Epicurus, was revived by Dalton, to prove these laws ; and 

 the electro-chemical theory of Davy, that combination takes place in 

 consequence of the opposite electric states of the combining elements, 

 has thrown new light on these mysterious phenomena. To Sir 

 Humphry Davy, we are indebted, for the discovery of the metallic 

 bases of the alkalies, in 1807 : and his researches have been recently 

 extended by our countryman, Dr. Hare. The first discovery of the 

 vegetable alkalies was made in 1803, by Sertuerner, of Germany : 

 since which time, the progress of this science in all its divisions has 

 been extremely rapid ; though there is still room for new investiga- 

 tions. 



We proceed to give a brief outline of chemistry, under the heads 

 of Non-metallic, Metallic, Organic, and Analytic Chemistry. 



1. Under the head of Non-metallic Chemistry, we would in- 

 clude so much of this science as relates especially to the non-metallic 

 elements; which, for the most part, are gases, liquids, or light solids; 

 destitute of metallic lustre ; and non-conductors, or imperfect con- 

 ductors of heat and electricity. There are 55 elements, or simple 

 ponderable substances, now known to chemists ; 42 of which are 

 metals, including the newly-discovered metal Lataniurn ; and 13 are 

 non-metals, including Silicon. These elements, by uniting together, 

 form compounds, of which the material world chiefly consists. 

 Most of the elements are usually solid ; but it is supposed that by 

 intense heat, all the solids might be converted into liquids, and these 

 into gases ; and that by pressure and abstraction of heat, all gases 

 and liquids might be solidified. The elements, by combination, often 

 change their state ; as when oxygen gas unites with sulphur, forming 



