Heaviside's proof of his expansion theorem

J. J. Smith: I should like to refer to the paragraph third from the end of Mr. Vallarta's paper in which he states that Heaviside gave another alternative proof of his Expansion Formula. This is given in Heaviside's Electrical Papers, Vol. II, p. 226, in a footnote. As this seems to be another very important way of proving the expansion theorem, I shall take the liberty of quoting it in full, as follows: