Thomson's Si/stem of Chemishy. 131 



arithmetical rules for reducing the difFerent European scales to 

 each other. When he copied Biot's plan, in beginning the 

 subject of heat with expansion, because this furnished an instru- 

 mental aid of research, why did he not likewise copy, from that 

 philosopher, some instructions for making or verifying a ther- 

 mometer? " The reader has only to peruse the chemical part 

 of Biot's Traitede Physique, to perceive how very superior it is 

 to the parallel discussions in the last two editions of Dr. Thom- 

 son's system, published since*." If he has neglected Biot, and 

 Gay-Lussac on thermometers, he has been careful to give suffi- 

 cient prominence to Sir Charles Blagden's experiments on ex- 

 pansion. 



The only alterations of any consequence, which the Doctor 

 has introduced into his first seven sections on heat, are a few 

 extracts from the papers of Dulong and Petit, and of Ure and 

 Southern ; the first chiefly on the laws of cooling, and the second, 

 on the elasticity of steam and other vapours. His eighth section 

 treats of the sources of heat, which are referred to six heads ; 

 the sun, combustion, percussion, friction, chemical combination, 

 and electricity. He ought to have included combustion under 

 chemical combination, of which it is merely an accident ; and he 

 should have enrolled decomposition among the sources of heat, 

 as we see in the cases of euchlorine, chloride and iodide of azote, 

 and in fulminating silver, gold, and platina. Under the second 

 head, combustion, we had hoped he would have indemnified the 

 public, in the present edition, for the obsolete and useless mat- 

 ter contained in the last. But we have been grievously dis- 

 appointed. Only nineteen pages are allotted to this most 

 important subject, of which not more than three are new 

 written. These are taken from Sir H. Davy's admirable re- 

 searches on flame, published some years ago in the Philoso- 

 phical Transactions. But the whole spirit of the original me~ 

 raoirs has been dissipated. What remains is a mere caput 

 mortuum, calculated to convey the most inadequate ideas of 

 Sir H. Davy's discoveries. Dr. Thomson's first sixteen pages 

 on this subject are absolute verbiage, to which the reproof of 

 Lord Bacon, is more strictly applicable, than to any modern 

 speculations which we know. " Et certc habent id quod puero- 

 rum est ; ut ad garriendum prompti sint, generare autcm non 

 possint : Nam verbosa videtur sapientia eorum, et operum 

 sterilis^." The exploded and unjjrofitable fancies of Stahl, 

 Priestley,' Crawford, Kirwan, Lavoisier, Brugnatelli, and Thom- 

 son, are given with nauseous prolixity; but the experimental 

 researches of Sir H. Davy, incouiparably more beautiful, and 

 full of fruit, are curtailed of their lair proportion, and discredit- 

 ably travestied. 



* Slightly altered from Dr. 'i'homson's wortls in his AimaU. 

 f Novum (Jriiunum, Lib. I. Ai)li. 71. 



K2 



