The Evolution of Chemistry. 129 



two men who ever were greater benefactors than Priestley 

 and Lavoisier. What was their meed for the good they 

 did ? Did they form a Bell-Berliner-Edison combine and 

 mount into fortunes therefrom ? Did their respective Govern- 

 ments shower favors on their heads ? No ! Priestley's the- 

 ology being distasteful to his neighbors, they made a bon- 

 fire of his home, his library, and his laboratory, and com- 

 pelled him to seek peace by leaving England and fleeing 

 to America. Lavoisier was unlucky enough to have been 

 born rich, and the freethinking, communistic cranks who 

 rode into power by the French Devolution could not stand 

 a crime so hideous, and so they cut his head off with the 

 guillotine. 



With the advent of Lavoisier's theory came a revolution 

 in chemical nomenclature. Up to this time names were 

 given to substances in the most arbitrary manner. Erratic, 

 fanciful, and unsystematic titles were the rule. After this 

 an effort was made to make the title tell something about 

 the structure of the substance bearing it. Bodies that de- 

 fied the chemist's power of decomposition usually retained 

 the old names, but such as were found to be compound had 

 their names made to fit their structures. Direct unions 

 with oxygen, chlorine, iodine, and the like were called ox- 

 ides, chlorides, or iodides of the substance thus uniting. 

 Acids bore suffixes that indicated the relative quantities of 

 oxygen in each, as sulphurous and sulphuric acids. Salts 

 from these acids were called, respectively, sulphites and sul- 

 phates. Improvement has gone on in this direction ever 

 since, and will probably keep going on for a long time to come. 



A new world for the chemist was opened up, and the 

 close of the eighteenth century was as fruitful of discovery 

 in this department of knowledge as had been the sixteenth 

 century in geography. Cavendish introduced the pneu- 

 matic trough, Bergman the blowpipe, and Davy the electric 

 battery, as instruments of investigation. Wenzel, Richter, 

 and Cavendish showed that in every chemical union a defi- 

 nite weight of one substance is necessary to saturate a given 

 weight of another. You may mix substances in all con- 

 ceivable proportions, but they never chemically unite except 

 in certain definite proportions. Any excess beyond the 

 weight Nature fixes is simply left over unchanged. Dalton, 

 however, found that if sixteen ounces of one of the ingre- 

 dients made perfect saturation and there happened to be 

 two compounds with the same ingredients, the second com- 

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