ANNIVERSARY ADDRESS. 31 



attack which a little latter led to its complete overthrow by F. 

 Hoffmann [1660 - 1742]. According to Ernst Meyer, 1 the history 

 of chemistry proper commences with Boyle, forasmuch as he 

 taught that the immediate object of the science was the acquisition 

 ■of a knowledge of the composition of bodies. Though prior to his 

 life and work, a considerable mass of isolated chemical facts was 

 being acquired, it was in the crucible of Lavoisier's mind [1743 - 

 1794] that they were transmuted into something like the gold of 

 true science. The greatest and most fruitful conception in the 

 •early development of chemistry was the atomic theory, which 

 arising chiefly out of Richter's 2 doctrine of chemical proportions 

 published about 1792, and Proust's 3 work confirmatory of the 

 same, took definite form in Dalton's mind in 1804, when he com- 

 municated the conception to Thomson. The latter published it in 

 his 'System of Chemistry' in 1807. This theory, viz., that every 

 •element is made up of homogeneous atoms of constant weight, 

 and that compounds are formed by the union of these in the 

 simplest numerical proportions, may be said to be the real 

 foundation of the whole science of Chemistry. In 1808 Gay- 

 Lussac [1778 — 1850] defined the law of gaseous combination by 

 volume, and in 1811 Avogadro [1776-1856] enunciated the 

 hypothesis that under the same conditions of temperature and 

 pressure, equal volumes of gases contain the same number of 

 molecules, an hypothesis espoused three years later also by 

 Ampere, and which has played a signal part in the development 

 of the science. These laws and hypotheses together with Charles' 

 law, discovered about 1786, connecting volume and temperature, 

 .and Boyle and Mariotte's 4 law connecting pressure and volume, 

 constitute the foundation of the physico-chemical theory of gases. 

 The next great step was the founding in 1852 by Frankland [born 

 1825] of the doctrine of the saturation-capacity or valency of the 

 ■elements, a doctrine which reached a fuller expression in Kekule's 

 ttheory of the 'linking of the atoms.' The theory of valency is 



1 History of Chemistry, 1898. 



2 [1762 - 1807]. 3 [1755 - 1826]. * Died 1684. 



