on the specific heats of Metals. 267 



gold and silver, two of the metals for which he has given new, 

 and, as he considers, more correct results, are as follow : 



1st Exp. 2d Exp. Difference. 



Specific heat of silver, - .0601 .0669 .0068 



gold, = .0375 .0509 .0134 



On comparing these differences with those given above, we find 

 that Mr Potter's two results differ nearly as much from one 

 another as the mean of them differs from the results of MM. 

 Dulong and Petit. Mr Potter adopts the mean of his two ex- 

 periments, supposing, fairly enough, that the methods being in- 

 verse, the errors are likely to have opposite signs. 



But, in the materials employed by Mr Potter, we shall find, 

 I conceive, ample cause for rejecting, without farther hesitation, 

 the specific heat assigned by him for these two metals. " For 

 gold, silver, and copper,"" he says, " I employed British coins ;" 

 that is to say, his gold was 22 carats fine, or an alloy containing 

 T ' 2 th of silver or copper ; and his silver contained 7.5 per cent, 

 of copper, — the quantities, I believe, usually found in British 

 coin. With these he attempted to determine the specific heats 

 of pure gold and silver; and because the result he obtained 

 differs from that of MM. Dulong and Petit, is it right in him 

 to denounce theirs as erroneous ? 



Rejecting these two alloys, then, there remains only the spe- 

 cific heat of bismuth to be considered. Mr Potter's two expe- 

 riments on this metal agree closely with each other ; the two 

 results being .0390, and .0393, while that of Dulong and Petit, 

 as above stated, is .0288. It will be necessary, therefore, to 

 advert to the concluding portion of Mr Potter's paper, before 

 we can determine absolutely which of them is to be preferred. 



It was the numerous mistakes contained in this latter part of 

 tin: paper, together with the tone improperly as well as unjust- 

 ly assumed towards the French philosophers, that suggested to 

 me the propriety of the present remarks. Admiring, as all must 

 do, the profound reasoning and exceeding ingenuity of Mr 

 Dalton, in his New System of Chemical Philosophy, Mr Pot- 

 ter has entered into his views not only regarding heat, but also 

 retrardinc the atomic weights of bodies, for which his book can- 

 not now lie considered as any authority. Had Mr Potter's 

 chemical reading been a little more extensive, he would neither 



