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“ On a Modification of Bunsen’s Calorimeter/’ by Professor 
Balfour Stewart, LL.D., F.R.S. 
One object of the calorimeter devised by Professor Bunsen 
is to measure the amount of heat given out by a small body 
when cooled from the ordinary temperature of the air to 0°C. 
For this purpose the body is dropped into ice-cold water 
contained in a small tube which is then closed with a cork 
to prevent change of air. Now the weight of the body being 
small compared with that of the ice-cold water into which 
it is plunged, the temperature of the latter never reaches 4°C. 
or the point of maximum density of water. The heated 
water will therefore be specifically heavier than that above 
it and will remain at the bottom. Nothing can be better 
than this arrangement for preventing the dissipation of the 
communicated heat by convection or otherwise, but the 
method employed by Bunsen of utilizing this heat has 
proved difficult in practice. It is well known that he makes 
use of this heat to melt ice contained in a vessel surrounding 
the bottom of his tube and measures the change of volume 
produced by the melting of the ice. 
I should propose to surround this tube with mercury 
instead of ice. In the above diagram t represents the tube 
and M a vessel full of mercury into which the tube is tightly 
inserted, the mouth of the tube extending above this vessel 
