302 MR. E. H. GRIFFITHS ON THE LATENT 
I have included in the above table all the experiments with the exception of two, 
which were performed on the same day (September 3rd), and whose extreme diver- 
gence from the others led to the discovery that the insulation of one of the leads had 
fallen off. In consequence, the value of R, was uncertain. Between September 3rd 
and 11th the whole apparatus was taken to pieces and fitted with new leads and 
insulators. From this time onwards the calorimeter was filled with oil in place 
of aniline (see Paper A., p. 77). 
I think it is evident that the discrepancies are greater than can be accounted for 
by errors in weighing, as they sometimes amount to nearly 1 per cent. 
I at first suspected that some moisture was escaping uncaught by the weighing 
bulbs, or that the entering air was not dry. I believe, for two reasons, that this was not 
the case. (1) The P,O; bulb, through which the gas finally passed, in no case increased 
in weight by as much as 0°0040 gram, and usually only by about 0°0020 gram, which 
showed how completely the moisture had been removed by the H,SO, (2) Before 
entering the apparatus the gas passed also through H,SO, and P,O,, therefore any 
quantity of moisture which escaped these drying agents would be likely to also escape 
the similar agents at the exit-end, and thus would not affect their weight. I had 
good evidence that this was the case, for I thoroughly dried the flask and tubes at a 
temperature of 40°, and then passed the gas through the apparatus into the weighing 
bulbs for an hour and a half; but the increase of weight in that time was not as much 
as 0005 gram. Again, if the gas was more completely dried at one end than at the 
other, the effect would have been to make all the values of L too low or too high. nOn 
course, I was entirely in the dark at the time of these experiments as to the real 
value of L, but I now find that the mean of each group gives a close approximation 
to the true value, hence there was no permanent raising or lowering cause at work, 
It will be noticed that the rate of flow of air was greatly changed during these 
experiments ; when three cells were used the rate of evaporation had to be nine 
times as great as when the D.P. was that of one cell. Inspection of the table will 
show that the variations in the values of L do not appear to be functions of the rate. 
For some time I fancied that “ priming” might be taking place, but, if so, the 
experiments with a rapid flow would probably all have given lower values than those 
with a slow flow, the carrying of particles of unevaporated water being much more 
probable when the velocity of the gas current was increased nine times. 
Again, it has been suggested that, as the pressure of the gas diminished during its 
passage through the apparatus, some heat would in consequence disappear. I would 
point out that the only constricted portions of the passage (after the air had once 
entered the tank) were within the calorimeter, and, if all the work done by the gas 
was performed within the calorimeter, the cooling, owing to expansion, would be just 
balanced by the warming of the tubes at the constricted points. Also, a persistent 
lowering of the values of L would be caused, and (as above pointed out) I now find 
that such is not the case. To test this matter at the time, however, I observed the 
