406 
MK.'E. H. GRIFFITHS ON THE VALUE OF 
Table IX.^ 
The following numbers were plotted:— 
1 
i 
' 
, 
aR 
cR deduced from 
(Legal ohms.) 
cR = •00422w2. 
No. of cells. 
Increase. 
0 
— X 
0 
0 
1 
0 
■0042 
•0042 
2 
•0120 
•0163 
•0168 ; 
3 
•0333 
: -0376 
•0378 , i 
4 
•0638 
•0681 
•0675 
5 
•1023 
•1066 
•1055 
6 
•1478 
•1516 
•1519 
Hence x — ‘0042, 
and the above agree within the limits of experimental error with the parabola 
8R = '00422 X ; where n is number of Clark’s cells. 
In this case there can be no doubt about the actual D.P. at the ends of the coil. 
The results of the previous investigation (p. 404) are of great importance, in so far as 
they confirm the conclusion that 814 = aE^, but are of little use for determining the 
value of a. 
In order to complete these experiments variations in the rate of stirring were tried. 
It was found, as would be expected, that the more perfect the stirring, the less the 
wire became heated ; but, within the limits of our rate of stirring, the change was so 
slight that no correction was thought necessary. 
The observer at the high-resistance galvanometer could, however, always detect 
minute changes in the rate of stirring by the irregular behaviour of the spot. These 
changes, although thus rendered very evident, had an exceedingly small effect and 
thus they served as a proof that the oscillations observed during our J experiments 
also indicated variations too minute to affect our measurements. 
[Note.— As illustrating the importance, as also the accuracy, of the correction 
rendered necessary by the difference between the temperature of the wire and of the 
water, we here give a summary of the results of J 9 and J 34. These two experi¬ 
ments were performed in order to subject the corrections (both for radiation, &c., and 
for the difference in the temperature of the wire) to a severe test, the heat 
developed per second in the wire during J 34 being nine times as great as that 
developed per second throughout J 9. 
* In comparing the last two columns, it must be remembered that a difference of ‘0010 corresponds to 
a difference of but I in 8600 in R. 
