Mr Potter on the Specific Heats of' Metals, $b. 79 



I used British coins, where it was needful that there should be 

 many pieces to have the requisite weight. This, it will be 

 readily seen, is rather an advantage than a disadvantage in using 

 the second method. I have moreover found, that, with a ves- 

 sel of the capacity of the above, it was necessary to operate 

 with at least about 1200 grains of metal to perform a good 

 experiment. The numbers in the table for lead were obtained 

 by immersing 8000 grains of the metal in 2000 grains of water. 

 As this metal appears to have the smallest capacity of any 

 metal known, I was anxious to determine it with accuracy, and 

 particularly from having previously made several trials which 

 did not accord very well together. When it can be practised, 

 I should recommend future experimenters to follow the same 

 plan, and use a greater weight of the substance which has the 

 least capacity, more especially when they wish to obtain good 

 approximations. These experiments show that .032 is very 

 near the correct number for lead at common temperatures, as 

 Mr Dalton's later experiments indicate. — See the Appendix to 

 the first part of the second volume of his chemical work. 



The thermometer which I have used I proved by breaking 

 the column of mercury in the tube, and measuring the number 

 of degrees which the separated length subtended in different 

 parts of the scale, and found it very nearly correct between 

 32° and 212°. 



Steel, (hard,) 

 (soft,) 



Zinc, 



Copper, 



Silver, 

 1 in. 



Weight 

 used. 



2014 grs. 



1032 



2017 

 1717 

 2111 

 2107 



v. 

 o 



u 



<J 



-9. 



3 



8 



11 



11 



<> 



1 



Specific heats from 

 the first method, or 

 the metal at 212° 

 immersed in water 

 at about 50°. 



For equal weights. 

 .102 1 ' 



.1086 



.1080 



.0912 



.0948 



.08GK 



.0601 



.059<i 



.0597 



Specific heats from 

 second method, or 

 the metal at about 

 45° immersed in 

 water at about 

 110°. 



For equal weights. 



.115 



.1084 



.1014 



.0660 

 .0542 

 .0588 



