Symbol for Partial Differentiation

Abstract

IN his first letter (p. 53), Prof. Perry very properly drew attention to the desirability of greater definiteness in the notation for partial differential coefficients in the case of functions of two variables, the essence of his remarks being that it is not enough merely to change d into ∂, but that the variable which is for the nonce held to be constant should also be indicated. Apropos of this, and for the sake of historical interest, I quoted from a paper since published (Proc. R.S. Edinb xxiv. pp. 151–194) a short paragraph regarding a passage¹ in Jacobi's writings of the year 1841, and containing a footnote with an old suggestion on the matter of notation. In his second letter (p. 271), Prof. Perry undertakes to show that this latter notation is objectionable so far as thermodynamics is concerned, and not to be compared with that which he himself uses. I regret to have to say that I was quite satisfied with his notation, and had no intention whatever of bringing the two into comparison, mine having been designed for much more complicated cases than those which occur in ordinary text-books on thermodynamics. His words are:—