4 



KNOWLEDGE. 



[January 1, 1897. 



Most of the chemical elements were discovered before 

 the year 1837. Five elements were discovered from the 

 year 1839 to 1844, and five others were subsequently 

 added after the general introduction of spectrum analysis. 

 Dalton, in 1808, published the first volume of his new 

 system of chemical philosophy, in which he placed the 

 atomic theory on a firm basis, and established once for 

 all the law of multiple proportions. Before Dalton's time 

 chemistry consisted of a heterogeneous mass of separate 



chemistry became for the first time an exact science. 

 Davy had laid down the laws of electro-chemical decom- 

 position, and by their application discovered metals of the 

 alkalies and alkaline earths ; while in 181G he bequeathed 

 to the mining world his safety-lamp, which has served 

 the double purpose of preserving life and increasing 

 commerce. In 1828 Wohler broke down the barrier which 

 was long supposed to exist between inorganic and organic 

 substances. It was thought that organic substances could 





George Stephenson's " Rocket" (1829), the Forerunner of the Modern Locomotive Engine. 

 {Hcijioditcf.d fi-oin the Ci^inji-i'jht Coloured Plate hu ^ermisr.ion of the Leadenhall Pixss^ Ltmited.) 



facts. The truth that chemical union between dissimilar 

 bodies will only take place in absolutely unalterable pro- 

 portions, as distinct from mechanical mixtures, is as 

 imposing in grandeur as the law of gravitation itself. To 

 follow the bearintrs of this great discovery in chemical 

 science would be to reveal all the operations of the 

 analytical chemist, and to exhibit the disparity between 

 a scientific chemical manufacturer and the rule-of-thumb 

 operator. By the promulgation of Dalton's views 



only be produced in the living bodies of plants and animals 

 requiring for their construction not only chemical affinities, 

 but a supposed rltnl force. But Wohler opened the way 

 to a new field of scientific investigation by producing urea 

 synthetically — that is, by building it up from its inorganic 

 constituents. Allen had proved the identity of the diamond 

 with charcoal ; while quite recently, it may be mentioned, 

 Moissan has accomplished the extraordinary feat of trans- 

 forming carbon from the amorphous to the crystalline 



