ON THE SPECIFIC HEAT OF WATER. 



207 



jlass having a capacity of alxmt three and a half litres. The Dewar vessel is held 



I iy means of a copper clip B in a hath with plate-glass sides (not shown), which is 



filled with wut IT nearly up to the top of the clip. The Dewar vessel is closed 



by a wooden lid D which carries the obturator E (separately shown in fig. 2), 



which is suspended from the lid by means of the three tul)68 G, G, H, which 



communicate with the interior of the obturator. The obturator contains water which 



is introduced through one of the tubes G and is 



heated by an electric heater of wire (not shown) 



to which leads K pass through the other tulx\ 



A thermometer inserted in the tube H shows the 



temperature of the water in the obturator. A 



baffle plate F is attached to the underside of the 



obturator. The obturator is furnished with six 



tubular openings and the baffle plate is pierced 



with holes to correspond. Through the centre hole 



passes a glass rod which carries at the lower end a 



stirrer and at the upper end a pulley, by means of 



which the stirrer is constantly rotated at a speed 



Fig. 2. 



Fig. 3. 



of 340 revolutions per minute. The front pair of tul)es served for the insertion of two 

 standard thermometers in the point-to-point experiments, but in the continuous flow 

 experiments the outflow pipe LL passed through one of the front tubes, whilst the 

 inflow pipe M (which is shown separately in fig. 3) passed through the back tube of 

 the obturator. The other tubes served for passage of the tubular glass leads NN of 

 tlie mercury thermometer-resistance, which is shown clearly in fig. 1, and forms the 

 electrical heater of the contents of the calorimeter. This thermometer- resistance 



