HEAT OF EVAPORATION OF WATER. 341 
Fig. 4 shows the method of insulating the leads where they passed through the lid of 
the calorimeter at / and /’ (fig. 3), and also the insulation of the four leads 
where they passed through the steel lid (see small sketch, Plate 6, fig. 3). 
PLATE 6. 
Fig. 1 is diagrammatic only, for the various tubes, &c., repeatedly crossed each other. 
The gas on entering passed through H,SO, at 8, then through P,O; at P, 
afterwards through the 30 ft. coil indicated at C, and thus attained to the 
temperature of the tank water. M, is an open scale manometer to show 
the pressure of the gas when entering the flask F. Leaving this flask near 
the top, the vapour traversed the coil C, and thus attained the temperature 
of the calorimeter; it then passed through the four-way tap T,, and on 
emerging from the tank passed over a row of small gas jets, shown at G. 
The tubes between T, and B could be swept by dry air, by use of the taps 
T, and T,. All the apparatus within the dotted lines was immersed in the 
tank water. 
Fig. 2 shows the arrangements of the differential thermometers and the bridge. 
The coil of AB is in series with the compensators of CD and vice versd. 
Fig. 3 shows the electrical connections with the calorimeter coil. 
A coil in the tank at F was of the same resistance and wire as the 
calorimeter coil. By means of the key K, the current could be switched on 
to either coil. K, was also connected with the chronograph in such a 
manner that all its movements were recorded. 
By means of the Rheochord the external resistance of the storage circuit 
(leads 2 and 4) could be so adjusted that the D.P. at the points M and 
N was always that of the Clark cells. Wires numbered 1 and 3 are in the 
Clark cell circuit. 
