364 Analysis of Scientific Books and Memoir!t^ 



gen be to azote as 7 to 6, but a product of .393 if oxygen be to azote as 7 

 to 10 : by Dr Thomson's ratio of oxygen to azote, 4 to 7, the product will 

 be .482, very different from .375. Hydrogen will give a product of .47 or 

 .41 instead of .375. All these diflPerences, it may be said, are occasioned 

 by errors in the specific heats of the gases ; but if errors of this magnitude 

 can still subsist after all the care that has been taken, we shall scarcely 

 know what to trust in experimental philosophy." Pp. 293, 294. 



Independent of these inconsistencies, we have grave reason for not ad- 

 mitting the accuracy of Messrs Dulong and Petit's table ; and our reason is 

 simply, that this table consists merely of results (sufficiently different from 

 former ones) without the authors having given any details of their experi- 

 ments even yet nine years after their publication ; so that, forsooth, we are 

 left to pin our faith not merely to the honour but to the immaculate accu- 

 racy of Messrs Dulong and Petit ; for they have taken effectual measures of 

 preventing the repetition of their experiments by others to confirm or to 

 disprove them. Do we doubt their experiments ? We are without evi- 

 dence ; and therefore we do not doubt them : We are without evidence ; 

 and therefore we do not believe them. But we protest against regarding 

 the experiments as ever made, till the authors enable others to repeat them. 

 We cannot help wondering at Dr Berzelius having allowed himself recent- 

 ly to be carried away by this flimsy table, so far as to assign three times 

 the atomic weight to bismuth that he otherwise would, especially when he 

 admits the atomic weight of cobalt to be a-half more than that assigned by 

 Messrs Dulong ajid Petit ; and the atomic weight of silver to be twice as 

 much. 



Having thus endeavoured to give some idea of the nature and merits of 

 the volume before us, we take leave of it, recommending it to the attention 

 of our chemical readers. The work is one which will not be read as an in- 

 troduction to chemistry ; but it will be perused with interest by all who 

 have made some progress in the science, and who make its doctrines a sub- 

 ject of habitual reflection. Of almost any other chemist than Mr Dalton, 

 we would have complained of the ignorance in which, it is evident, he has 

 kept himself of the researches of other chemists. But we cannot speak in 

 the language of complaint of Mr Dalton, known to the world as a very 

 apostle of science — leaving all worldly advantage behind to follow it, and 

 proceeding on cheerfully, without scrip, or purse, or staff. We know not 

 how to express the feelings with which we glance over the last three pages 

 of this volume, containing a list of the scientific papers which Mr Dalton 

 has published during a period of thirty-five years. One discovery of his 

 gives a glory to the scientific character of the nation ; independent of other 

 discoveries which alone would rank him high as a philosopher. And for 

 whose good ? We cannot look to this list without believing that Mr Dal- 

 ton is tnore likely to have lost money than to have gained by all his publi- 

 cations. In other countries, less happily constituted governments than our 

 own would not have hesitated to put into the hands of such a man the 

 means of prosecuting with independence those discoveries which in all after 

 agos were to render his native land illustrious among civihzed nations. 

 Almost the only means of profit held out to scientific men in this country 



