Report on the Progress of Chemistry. 



145 



of London, felt warranted in making the very strong dec- 

 laration that "the existence of atoms is the life of chem- 

 istry." And yet the truth of the atomic theory is not 

 unquestioned. Sir Benjamin Brodie seems to quite re- 

 ject it, while he points out what he regards as a better basis 

 of the science. Dr. Odlingand Dr. Frankland also agree 

 with Sir Benjamin that the facts of chemistry, while they 

 may be explained by it, do neither prove nor require the 

 atomic theory. Dr. Roscoe, in his address before the che- 

 mical sectiou of the British Association (meeting of 1870), 

 after reviewing the opinions of the gentlemen just named, 

 gave expression to what, doubtless, may be considered as 

 the sentiment at present of the majority of chemists. While 

 he seems to hold himself in readiness to give up the atomic 

 theory, whenever anything better may be offered in its 

 place, he yet declares that its assumptions explain the facts 

 of chemistry, as the undulatory theory gives a clear view 

 of the phenomena of light. 



Next to the atomic theory, the doctrine of quantivalence, 

 or, as it is also called, atomicities, is the most important in 

 modern chemistry. The introduction of this theory is of 

 recent date, and it has wrought a thorough revolution of the 

 science, overturning the older views of chemical compo- 

 sition, and even banishing the familiar La voisierian nomen- 

 clature. 



As far back as the year. 1851, the germ of this theory ap- 

 peared in the attempt of Dr. Williamson to group bodies 

 into classes founded upon their resemblance in composition 

 to some other body regarded as a type. The oxygen 

 acids, bases and salts, in his view, belonged to a single 

 group whose typical compound is water. In 1853, Ger- 

 hardt added hydrogen and ammonia to the list, and suc- 

 ceeded in classifying a great number of known compounds 

 under these three types. Hydrochloric acid was afterward 



Trans, vii.] 19 



