134 Analysis of Scientific Books, 



require refutation, especially as we have formerly paid our 

 respects to it*. If the rapid emission of heat and light, with 

 a change of properties in the bodies concerned, be not combus- 

 tion, we beg the Doctor to define what combustion is. 



In his meagre couple of pages on the heat produced by che- 

 mical combination, which is a verbatim re-print of the article 

 " Mixture," in the 5th Edition, he travesties M. Gay-Lussac. 

 " From the experiments of Gay-Lussac, it appears still more 

 clearly, that the evolution of heat or cold in such cases 

 depends upon the change of the water, from a state of so- 

 lidity to a state of liquidity, or vice vcrsd. He mixed toge- 

 ther a solution of nitrate cf ammonia of the specific gravity 

 1,302, at the temperature of 61°.3 with water, in the proportion 

 of 44.05 of the former, and 33.76 of the latter. The tempera- 

 ture of the mixture sunk 8°. 9, yet the density increased ; for 

 the mean density would have been 1.151, while the density of 

 the mixture was 1.159. This acute experimenter mehtions 

 several similar examples ; though in none of them was the 

 absorption of heat so great, as in the instance which I have 

 selected." Now, we ask the Doctor, what have these phseno- 

 mena to do with the change of water from a state of solidity to 

 a state of liquidity, or vice versd. We have two liquids mixed, 

 which continue liquid, and though the density be increased, heat 

 is not evolved but absorbed, to use our author's phraseology. 

 Compare with this fact his previous explanation. " It is not 

 difficult to see why condensation should occasion the evolution 

 of caloric and rarefaction the contrary. When the pai'ticles of a 

 body are forced nearer each other, the repulsive power of the 

 caloric combined with them is increased, and consequently a part 

 of it will be apt to fly ofFf." But it will be difficult, nay, impos- 

 sible for the Doctor, on these principles, to see why rarefaction 

 should occasion the evolution of caloric, and condensation the 

 contrary, as happens in the above indisputable experiments of 

 the French philosopher. 



His three pages on the sixth source of heat, electricity, are 

 also a re-print, and are remarkable only for the prominence 

 which they give to Berzelius's electric hypothesis of combustion, 

 a disfigured plagiarism in 1813, from Sir H. Davy's Bakerian 

 Lecture of 1806. Instead of quoting a crambe recocta of Doctor 

 Thomson, who admits that the compounds of oxygen with 

 chlorine, and phosphorus with sulphur, are " incompatible 

 with Berzelius's doctrine of chemical affinity taken in its broadest 

 extent ;" we shall give more satisfaction to our readers by the 

 following extract from the memoir of the learned Swede him- 

 self. " The chemical action effected by the discharge of the 



* Vol. IV., p. 30G'. 1 Si/^ttM, vol. I. p. 150. 



