280 MR. E. H. GRIFFITHS ON THE LATENT 
Exterior Connections. 
The upper end of the narrow glass entrance tube f (Plate 5, fig. 1) was, as before 
stated, connected with a glass single-way tap, T; (Plate 6, fig. 1), which, on the 
further side was connected with about 30 feet of thin-walled copper tubing immersed 
in the tank water. Thus, all gas entering the silver flask through T; would be 
at the temperature of the tank water, and (the calorimeter temperature being 
identical with that of the tank) no heat would be added or subtracted when gas was 
passed through the flask and spiral. T, was a four-way tap on the exit side, the 
arms of the one passage through its core being at right angles to each other. The 
tap is shown in fig. 1 (¢nfra). A is the tube leading from the flask and connected with e 
(Plate 5, fig. 1). By rotating the core, A could be connected with B or D, or C 
could be connected with B or D. ‘The glass tubes forming the outer case of both 
taps T,; and T, were sealed at the lower extremity, and after a portion of the tube 
above the core had been filled with mercury, these taps were perfectly air-tight. 
The outer glass tube of each was about 6 inches long, thus the lower 4 inches were 
below the surface of the tank water, and the upper parts of the tubes were packed 
with cotton wool. The cores narrowed to a glass rod, which, passing through the 
wool, projected above the tank lid, where a handle was attached ; thus the taps 
could be opened or shut from the exterior of the whole apparatus. The position of 
the taps is indicated in Plate 6, fig. 1. 
Tube B (fig. infra) which communicated with the apparatus into which, during 
my earlier experiments, the vapour was passed, extended under the surface of the 
water to the walls of the tank, it then passed above a row of small gas jets, and thus 
no condensation took place until the vapour arrived at the drying bulbs. At the close 
of an experiment a movement of the tap connected C and B, and as C was connected 
by a three-way tap (T,, Plate 6, fig. 1) with the dry air supply, any moist air 
remaining in B or its continuation was swept into the receiving apparatus. On the 
other hand, by connecting A and D before the commencement of an experiment the 
vapour brought by the gas which had passed through the calorimeter was disposed of 
without affecting the weight of the receiving apparatus attached to B. Thus an 
experiment could be started at any moment by changing the connection at tap T, 
from AD to AB, and that without altering in any way the conditions as to flow 
of gas, rate of evaporation, &c. 
Finally, I would remark that throughout the gas circuit, the yas only came into 
contact with the following materials—glass, silver (only hard solder was used for all 
the flask and tube connections), the glass-metal-joining alloy at the junctions, and the 
drying agents. True, in my “exhaust” experiments with water the vapour had to 
pass through about half-an-inch of thick rubber on the exit side, where connection was 
made with the condenser, but when using other liquids, this joint can easily be 
replaced by a glass one. When evaporating ether (with which I have made some 
