24 SPECIFIC HEAT. 



Specific heat. 



Iron 110 



Copper 95 



Zinc 93 



Silver 56 



Mercury 33 



Platinum 31 



Lead 29 



The method of cooling gives results so exact, as to allow the 

 detection of an increase of capacity with the temperature. The 

 capacity of iron, when tried between 32 and 212, as was the 

 case with all the bodies in the table, was 110 ; but 115 between 

 32 and 392, and 126 between 32 and 662. It hence fol- 

 lows, that the capacity for heat, like dilatation, augments in 

 proportion as the temperature is elevated. Dulong and Petit 

 likewise established a relation between the capacity for heat of 

 metallic bodies and the proportion by weight in which they 

 combine with oxygen, or any other substance, which will again 

 be adverted to. 



Of all liquid or solid bodies, water has much the greatest 

 capacity for heat. Hence the sea, which covers so large a pro- 

 portion of the globe, is a great magazine of heat, and has a 

 beneficial influence in equalizing atmospheric temperature. 

 Mercury has a small specific heat, so that it is quickly heated 

 or cooled, another property which recommends it as a liquid for 

 the thermometer, imparting, as it does, great sensibility to the 

 instrument. 



The determination of the specific heat of gases is a problem 

 involved in the greatest practical difficulties ; so that notwith- 

 standing its having occupied the attention of some of the ablest 

 chemists, our knowledge on the subject is still of the most 

 uncertain nature. It has been concluded by Delarive and 

 Marcet,* and by Mr. Haycraft,f that the specific heat of all 

 gases is the same for equal volumes. But this opinion has been 

 controverted by Dulong, J and by Dr. Apjohn ; and most che- 

 mists are now disposed to place more reliance upon the old 

 experiments of Delaroche and Berard than upon any others 



* Annales de Ch. et de Ph. t. 35, p. 5. and t. 4 l,p. 78. 



t Edinburgh Phil. Trans. 1824. 



I Annales de Ch. et de Ph. t. 41, p. 113. 



Transactions of the Royal Irish Academy, 1837. 



