; Chemistry. Xvi 
measute upon the accuracy of this opinion. Mr. Dalton, with- 
out any direct experiment, has taken it for granted as a conse- 
quence of his peculiar views respecting heat, that the specitic 
heat of every body increases with the temperature; while Dr. 
Ure, from a set of experiments given in his elaborate paper on 
heat, published in the Phil. Trans. for 181%, concludes, that the 
specific heat of bodies diminishes as the temperature increases. 
Dulong and Petit, in their prize dissertation, so frequently men- 
tioned in the preceding part of this sketch, have detailed a set of 
' experiments made upon cight different solid bodies on purpose to 
decide this long agitated question. ‘he experiments seem to 
have been made with great care. The method followed was the 
one originally suggested by Dr. Black, and followed by Dr. 
Crawford and Mr. Wilke. ‘The solid substance was raised to the 
requisite temperature by plunging it in oil or mercury, and then 
suddenly immersed in so great a quantity of water that this liquid 
was only elevated a few centigrade degrees by the heat commu- 
nicated by the solid. The water was contained ina thin vessel 
of tin-plate standing on four isolated points. In general, the 
water was cooled as many degrees below the temperature of the 
room as the solid was capable of raising it; and when this was 
_not the case, a correction was applied for the heat dissipated 
during the experiment. Knowing the weights and temperatures 
of the solid and the water before the experiment, and the change 
of temperature produced on the liquid by plunging the solid into 
it, it was easy to determine the specific heat of the solid; that 
of water being as usual reckoned unity. But the accuracy of 
such experiments depends upon the precision with which the 
temperatures are determined. Dulong and Petit employed a 
thermometer capable of indicating +1,th of a centigrade degree, 
and of such a size as to give the mean temperature of the liquid 
examined. The following table exhibits the specific heats of the 
different solids tried at the different temperatures indicated 
by a centigrade air thermometer. 
Specisic Hears. 
Solids. Between 0° ; Between0° | Between 0° ; Between 0° 
and 100°. and 200°. and 3009. and 350°. 
UNE taka oiela, © sl sipiii7 Oe LOGS 0°1150 0-1218 0°1255 
Mercury ......}. 0°0330 ate 0°0350 
SNC led eens st) 0:0927 or 0°1015 
Antimony. ....| 0°0507 or 0°0549 
Silver. ........] 0°0557 ae 0-0611 
Copper. ......| 0:0949 Ae 0°1013 
Platinum .....| 0°0355 , 0:0355 
Glass. pee Sa! 01770 ae 0:1900 
Vou, XIII. b 
