From these valuable papers it will be seen that the peculiar states of iron had already attracted attention, particularly those “inactive conditions” noticed in a “_Note sur la Manière d’agir de l’Acide nitrique sur le Fer, par J. F. W. Herschel_,” Aug. 1833; and previously indicated by M. H. Braconnot, _Sur quelques Propriétés de l’Acide nitrique_, Annales de Chimie, vol. lii. p. 54. Reference should also be made to the Memoirs of Sir John Herschel, _On the Action of the Rays of the Solar Spectrum on Vegetable Colours_, _&c._: Phil. Trans. vol. cxxxiii. p. 221; and _On the Separation of Iron from other Metals_: Phil. Trans. vol. cxi. p. 293; and several papers by Schönbein, in the Philosophical Magazine, from 1837. [33] Faraday, in his memoir _On new Magnetic Actions, and on the Magnetic Conditions of all Matter_, says:--“By the exertion of this new condition of force, the body moved may pass either along the magnetic lines or across them, and it may move along or across them in either or any direction, so that two portions of matter, simultaneously subject to this power, may be made to approach each other as if they were mutually attracted, or recede as if mutually repelled. All the phenomena resolve themselves into this, that a portion of such matter, when under magnetic action, tends to move from stronger to weaker places or points of force. When the substance is surrounded by lines of magnetic force of equal power on all sides, it does not tend to move, and is then in marked contradistinction with a linear current of electricity under the same circumstances.”--Phil. Trans. for 1846, vol. cxxxvii. [34] _New Experiments and Observations on Electricity made at Philadelphia, in America._--Addressed to Mr. Collinson, from 1747 to 1754. By Benjamin Franklin. Of these Priestley remarks:--“It is not easy to say whether we are most pleased with the simplicity and perspicuity with which the author proposes every hypothesis of his own, or the noble frankness with which he relates his mistakes, when they were corrected by subsequent experiments.” [35] “The atomic philosophy of Epicurus, in its mere physical contemplation, allows of nothing but matter and space, which are equally infinite and unbounded, which have equally existed from all eternity, and from different combinations of which every visible form is created. These elementary principles have no common property with each other; for whatever matter is, that space is the reverse of; and whatever space is, matter is the contrary to. The actual solid part of all bodies, therefore, are matter, their actual pores space, and the parts which are not altogether solid, but an intermixture of solidity and pore, are space and matter combined.