August 28, 1896.] 



SCIENCE. 



245 



atomic theory, and had obtained the j&rst 

 experimental evidence on a matter which 

 had enlisted attention for more than two 

 thousand years, Davy showed, by brilliant 

 experiments, that certain bodies were com- 

 pounds, although they had resisted all pre- 

 vious attempts to decompose them. Since 

 the first use of electricity had so important 

 results, men were ready to suspect that 

 even supposed elements might ultimately 

 prove to be compounds. It was therefore 

 in a congenial soil that Front's hypothesis 

 took root. Trusting to experiments of not 

 much accuracy, Prout suggested, in the 

 year 1815, that probably the atomic weights 

 of other elements were divisible, without 

 remainder, by the atomic weights of hydro- 

 gen ; or, in other words, that they are whole 

 numbers, if the atomic weight of hydrogen 

 be taken as unity. 



The new suggestion was most attractive, 

 for two reasons: On the one hand, the 

 truth of the new suggestion would lead to 

 a very great practical advantage. The 

 labor of determining atomic weights would 

 be immensely simplified and lessened if we 

 could know beforehand that the numbers to 

 be found were integers. And, on the other 

 hand, the new suggestion, if approved, 

 would promise a most interesting and val- 

 uable hint as to the nature of matter and 

 the structure of atoms. If, for instance, 

 the atoms of carbon and nitrogen and oxy- 

 gen weigh precisely as much as twelve and 

 fourteen and sixteen atoms of hydrogen, 

 then it is a very plausible hypothesis that 

 each of these atoms is really composed of 

 the material of twelve and fourteen and 

 sixteen atoms of hydrogen, compacted into 

 a new atom. Davy had led many to sus- 

 pect that perhaps some atoms might be 

 compound, and the new suggestion, looking 

 in the same direction, was received with 

 favor by many, among whom were great 

 discoverers, and great experimenters, and 

 great teachers of chemistry. In England, 



where Davy and Prout both lived, Thom- 

 son had great influence. It was Thomson 

 who, in the Journal of Chemistry, of which 

 he was the editor, first announced Dalton's 

 discovery. Thomson wrote the history of 

 chemistry. Thomson's ' System of Chem- 

 istry ' was thought worthy of translation 

 into French at a time when French was the 

 mother tongue of chemistry. And Thom- 

 son accepted Prout's hypothesis as probably 

 true. But Turner made more accurate and 

 more numerous determinations of atomic 

 weights than any other English chemist ; 

 and he rejected Prout's hypothesis. Ber- 

 zelius, the great Swedish chemist, whose 

 determinations of the atomic weights of 

 all the elements then known were regarded 

 with so much admiration by all chemists, 

 pronounced Prout's hypothesis a pure illu- 

 sion. But Dumas, than whom none in 

 France stood higher, whose opinion had 

 great weight on account of the excellence 

 of his many determinations of atomic 

 weights, accepted Prout's hypothesis with 

 a slight modification, and believed that his 

 experiments had established its truth. Stas, 

 the distinguished pupil of Dumas, began 

 his work with a bias in favor of the hypoth- 

 esis; but when his first series of admirable 

 determinations of atomic weights was pub- 

 lished, he pronounced the hypothesis a pure 

 illusion, entirely irreconcilable with the 

 numerical results of experiment. But Mal- 

 let, who has made several excellent deter- 

 minations of atomic weights, and Clarke, 

 who has recomputed and reduced to order 

 all the published determinations, declared 

 themselves forced to give Prout's hypoth- 

 esis a most respectful consideration. It is 

 obvious, then, that ten years ago it was not 

 finally settled whether the hypothesis was 

 or was not true. 



The hypothesis, then, has disappointed 

 our hopes of any practical advantage in 

 conducting to a knowledge of the exact 

 value of any atomic weight. But neverthe- 



