Note 21 — PREFACE TO THE SECOND EDITION.

Sir W. Thomson’s words are as follows (Cambridge Mathematical Journal, Nov. 1842, vol. iii. p. 174). “When x is negative, the state represented cannot be the result of any possible distribution of temperature which has previously existed.” There is no limitation in the sentence to the laws of conduction, but, as the whole paper treats of the results of conduction in a solid, it may no doubt be understood that there is a tacit limitation. See also a second paper on the subject in the same journal for February, 1844, vol. iv. p. 67, where again there is no expressed limitation.