ON THE MECHANICAL EQUIVALENT OF HEAT 



359 



The change of the temperature was effected by means of a Bunsen 

 burner under the vessel w. 



The working of the apparatus was as follows: The temperature 

 having been raised to the required point, the piston q was worked to 

 stir up the water; this it did by drawing the water through the holes 



"31 



FIG. 1. 



FIG. 2. 



at c I and the perforated diaphragm s, and thence up through the 

 apparatus to return on the outside. When the whole of the water is 

 at a nearly uniform temperature the stirring is stopped, the valve op 

 falls into place, and the connection of the water in the outer and inner 

 vessels is practically closed as far as currents are concerned, and be- 

 fore the water inside can cool a little the outer water must have cooled 

 considerably. 



