16G Reviews. 



realized very clearly the existence of what are now termed the 

 laws of Constant and of Reciprocal Proportion, but had disco- 

 vered the law of Multiple Proportion, which no one had even 

 suspected to exist, before he announced it ; and had in effect an- 

 nounced the equally important law of Compound Proportion, the 

 honour of proclaiming which no one disputes with him. 



Dr Henry also shows more fully than had been shown before, 

 that with an almost inexplicable perversity, Dalton insisted on 

 disbelieving in those beautiful laws of Combination by Measure, 

 which Gay-Lussac proved to obtain in the case of gases, and en- 

 titled the Theory of Gaseous Volumes, although it was the coun- 

 terpart of his own theory of Combination by Weight, and, as every 

 one now sees, confirmed and extended it. 



Dalton died a believer in the existence of atoms which " no 

 man can split." His biographer has marshalled with great ful- 

 ness and clearness all the arguments deducible from recent che- 

 mical discoveries and speculations, in support of the existence of 

 indivisible ultimate particles, or true atoms ; but he impartially 

 acknowledges that they cannot be demonstrated to exist, and con- 

 tents himself with urging the probability of their existence. The 

 important and much disputed question here raised, we shall not 

 discuss on this occasion, but all to wdiom it is interesting will find 

 new and valuable materials for its settlement in Dr Henry's work. 



It remains to add, that on the personelle of Dalton, of which 

 we have said nothing, ample and very interesting particulars are 

 furnished ; and that the volume is enriched by contributions from 

 many distinguished men of science. The Cavendish Society has 

 done a signal service in publishing a work so well written and so 

 valuable. 



The Principles of Harmony and Contrast of Colours, and 

 their Applications to the Arts. By M. E. Chevreul, 

 Membre de l'lnstitut de France, &c, &c. Translated from 

 the French by Charles Martel. London : Longman & Co. 

 1854. 



Chevreul is a remarkable example of distinction won in depart- 

 ments of enquiry so different, that posterity is likely to halve or 

 double him, and insist on the existence of at least of two Messieurs 

 Chevreul, the one famous amongst chemists, as the discoverer of 

 the true nature of Fatty bodies ; the other, a high authority among 

 Natural Philosophers and Artists, as a discoverer of new relations 

 among colours. There is, however, but one Chevreul, and his work 

 on colour, which sprang out of his labours as chemist to the Gobe- 



