208 MESSRS. W. B. BOUSFIELD AND W. ERIC BOUSFIELD 



consist* of a long spiral of glass tube which is fused at each end to the tubular leads 

 NN there Iwing at the points of fusion a short piece of platinum wire fused in winch 

 nukes electrical connection between the mercury with which the tubular leads are 

 filled and the mercury contained in the glass spiral. A thermometer tebe 

 furnished with a scale communicates with the spiral glass tube, and the mercury in 

 the spiral rises to a convenient height in the thermometer tube, so that the spiral 

 heater forms in effect the bulb of a thermometer, the indications of which can be 

 read off on the scale of the tube P. Thick wire leads dipping into the mercury in 

 the tubes N served to connect the heater electrically with the dynamo. 



The resistance of the heater was from 9 to 10 ohms, so that with a current of 

 about 5 amperes a heating effect equal to 230 to 250 watts was obtained. The bore 

 of the lead tubes NN was made of such a size (6 mm. diameter) that when using a 

 current of about 5 amperes, which would raise the contents of the calorimeter 

 (3 litres of water) at the rate of about 1 C. per minute, the heating effect of the 

 current on the mercury leads in the tubes should be approximately such as to raise 

 their temperature at the same rate. The portion of the mercury leads below the 

 baffle plate P was taken as forming part of the heater (see Section 5). 



Another mercury thermometer- resistance similar to the above, but of 2 mm. 

 internal diameter and only 2 ohms resistance, was used to determine the current in 

 conjunction with the standard cells. This is shown diagrammatically as M t in fig. 4, 

 but does not require further description. 



For the continuous flow experiments a large volume of water was required which 

 was brought into a large thermostat raised above the level of the calorimeter. A 

 large toluene mercury regulator of a modified Lowry type was used, and with this it 

 was easy to maintain the inflow water during a run of some hours at a practically 

 constant temperature (within 0'005 C.). This cistern, in which a constant level of 

 water was maintained, was connected with the calorimeter by a tube Q which 

 bifurcated into two branches a and b. As the obturator was maintained at a 

 temperature 10 C. above that of the calorimeter, it was necessary to provide for the 

 inflow water being passed through the obturator without sensible change of 

 temperature. The arrangement of the inflow by which this was secured is shown in 

 detail in fig. 3. The inflow water comes in through the tube a, round the thermo- 

 meter which indicates the inflow temperature, and passes down through the tube c 

 into the calorimeter and mixes with the water there, after passing through a bent 

 prolongation of the tube c, which is immersed in the calorimeter water so as to bring 

 it up to nearly the temperature of the contents of the calorimeter before mixture 

 therewith. The inflow water rises up to the level of tube d, and a slight excess 

 overflows through that tube. In this way .a sufficiently constant level and flow was 

 obtained. The volume of water which passes through the tube Q and thence through 

 tul ft is only about a tenth of that which passes from the tube Q through the tube I. 

 This latter water passes down through the jacket-tube surrounding the tube c and 



