MR. J. B. HANNAY ON A NEW CALORIMETER. 24<7 



of the instruments_, I give here some specific heats taken 

 at random from many I have done. 

 First by No. i Calorimeter : — 



Substance. Found. Ourrect numbers. 



Arsenic '0820 '0814 



Tin 0575 '05623 



Platinum '0339 "0335 



Bismuth '0315 '03084 



I should say that I took as my standards to draw the 

 reference-curve the following metals : — 



Lead -03065 



Silver -05701 



Zinc '09555 



Iron -11380 



lesium -24990 



The difterential calorimeter gave : — 



Substance. Found. Correct numbers. 



Arsenic "0818 -0814 



Tin '0565 -05623 



Platinum '0338 '03 3 5 



Bismuth -0309 -03084 



In conclusion_, I would say that the form of air-calori- 

 meter I have given as No. i is very well adapted for 

 teachings as it enables students to construct for themselves 

 instruments of sufficient exactitude to yield numbers very 

 closely agreeing with standard numbers ; while for calori- 

 metric investigations, where freedom from all error is the 

 first requisite, the differential calorimeter is very well 

 adapted. The latter may also be made with india-rubber 

 joints ; but, as there is pressure, I prefer to have the joints 

 hermetically sealed. In determining the heat of combi- 

 nation by these instruments^ the same relative method is 

 used as for specific heats. It will be obvious that one 



