profound astronomical knowledge; yet in the main it is to be found clearly expressed in Kant, and on account of the importance of the matter, would alone have been sufficient to make his name immortal. It cannot but disturb us very much if we find minds of the first order under suspicion of dishonesty, which would be a scandal to those of the lowest order. For we feel that theft is even more inexcusable in a rich man than in a poor one. We dare not, however, be silent; for here we are posterity, and must be just, as we hope that posterity will some day be just to us. Therefore, as a third example, I will add to these cases, that the fundamental thoughts of the “Metamorphosis of Plants,” by Goethe, were already expressed by Kaspar Wolff in 1764 in his “Theory of Generation,” p. 148, 229, 243, &c. Indeed, is it otherwise with the _system of gravitation_? the discovery of which is on the Continent of Europe always ascribed to Newton, while in England the learned at least know very well that it belongs to Robert Hooke, who in the year 1666, in a “Communication to the Royal Society,” expounds it quite distinctly, although only as an hypothesis and without proof. The principal passage of this communication is quoted in Dugald Stewart’s “Philosophy of the Human Mind,” and is probably taken from Robert Hooke’s Posthumous Works. The history of the matter, and how Newton got into difficulty by it, is also to be found in the “_Biographie Universelle_,” article Newton. Hooke’s priority is treated as an established fact in a short history of astronomy, _Quarterly Review_, August 1828. Further details on this subject are to be found in my “_Parerga_,” vol. ii., § 86 (second edition, § 88). The story of the fall of an apple is a fable as groundless as it is popular, and is quite without authority. (2) To No. 18 of Matter. _The quantity of a motion_ (_quantitas motus_, already in Descartes) is the product of the mass into the velocity.