476 
MR. E. H. GRIFFITHS ON THE VALUE OF 
ox two by an accident with the reversiag key; in No. 6, the chronograph refused to 
work throughout the first two ranges; in No. 10, some contact must have taken place 
between the wires of the coil, as the potential-halance was entirely destroyed after 
the 7th range. No. 11 was an exceptionally bad experiment, especially in the latter 
half; the changes in water pressure were so rapid and violent as to pass beyond the 
control of the motor-regulator, the rate changing from 29‘43 to 30'36 in two consecu¬ 
tive observations. Had it not been for our desire to present our results in f ull , we 
would certainly have rejected this experiment. 
Exipei^ments 13 to 19. {Gro^i^ E.) 
In this group, our heaviest weight, the observations although still somewhat 
irregular are in better agreement. As might be anticipated the throw of the stiri’er 
was less affected by the obstructions at the base when the depth of water was 
greater. The alterations made in the connections of the stirring rod have been 
already alluded to. 
Our conclusions as to the value of J and the changes in the specific heat of water 
are based almost entirely on the results of Series IT. Although the results deduced 
from Nos. 13 to 19 are in almost perfect harmony with those from Series II., the 
agreement, for the reasons given above, must be in part fortuitous. The mean value 
of J deduced from Nos. 5 to 12 agrees with the most probable value, but the change 
in the specific heat of water alters from positive to negative according as the group is 
compared with the results obtained from a lighter or a heavier weight. 
Series II. 
This series contains but fifteen experiments, which may appear a small number on 
which to base our conclusions. We would, however, point out that these are only 
the concluding series of many hundred J experiments conducted by the same 
observers, who are therefore in the best position to judge of their value. Further¬ 
more, these fifteen experiments are conducted on very different weights of water and 
with very different currents, and our conclusions would be but little altered if they 
were based on any two individual experiments rather than on the mean results of all. 
Want of time alone prevented our increasing their number, but we believe that such 
increase would have given them small additional weight. The results of Series I. are 
quite sufficient to corroborate the value of J, although the least trustworthy group 
of that series gives contradictory values for the change in specific heat of water. 
Such irregularities as are observable in the members of these series, are we believe 
inseparable from the use of mercury thermometers. Although many irregularities 
which would otherwise he apparent have been eliminated by the method of 
calibration adopted (Section X.), there yet remain residual ones, not strlctl}'' recurrent, 
whose effect can only be eliminated by taking the mean path of a series of obser¬ 
vations over consecutive ranges. The magnitude of such irregularities can be 
