3 ([return])
[ Fortnightly Review, April, 1875.]
4 ([return])
[ Jevons's Principles of Science, Vol. II. p. 145. The figures, which in the English system of numeration read as seventeen billions, would in the American system read as seventeen trillions.]
5 ([return])
[ Fortnightly Review, June, 1875, p. 784.]
6 ([return])
[ Babbage, Ninth Bridgewater Treatise, p. 115; Jevons, Principles of Science, Vol. II. p. 455.]
7 ([return])
[ See my Outlines of Cosmic Philosophy, Vol. II. pp. 142-148.]