Let us write our formula in the form
V(t+n) / Vt = xn .
Then choosing two values out of the above experimental series (say the second and the second-last), we have t = 23·5, n = 10, and V, V′ = 10·8 and 69·5 respectively.
Accordingly
69·5 / 10·8 = 6·4 = x10 .
Therefore
(log 6·4) / 10, or ·0806 = log x.
And,
x = 1·204 (for an interval of 1° C.).
This first approximation might be considerably improved by taking account of all the experimental values, two only of which we have as yet made use of; but even as it is, we see by Fig. [26] that it is in very fair accordance with the actual results of observation, within those particular limits of temperature to which the experiment is confined. {112}