_Dr. T. Sterry Hunt on the pre-nebular condition of matter._—A year after the foregoing views regarding chemical dissociation had been advanced by Sir Benjamin Brodie, Dr. T. Sterry Hunt, in a lecture on “The Chemistry of the Primeval Earth,” delivered at the Royal Institution (May 31, 1867), put forward, apparently quite independently, opinions on dissociation similar to those of Brodie. In this lecture he says: “I considered the chemistry of nebulæ, sun, and stars in the combined light of spectroscopic analysis and Deville’s researches on dissociation, and concluded with the generalisation that the breaking-up of compounds, or dissociation of elements, by intense heat is a principle of universal application, so that we may suppose that all the elements which make up the sun, or our planet, would, when so intensely heated as to be in the gaseous condition which all matter is capable of assuming, remain uncombined, that is to say, would exist together in the state of chemical elements, whose further dissociation in stellar or nebulous masses may even give us evidence of matter still more elemental than that revealed in the experiments of the laboratory, where we can only conjecture the compound nature of many of the so-called elementary substances.”[70] And in his address at the grave of Priestley he referred to the suggestion of Lavoisier that hydrogen, nitrogen, and oxygen, with heat and light, might be regarded as simpler forms of matter from which all others are derived. This suggestion was considered in connection with the fact that the nebulæ, which we conceive to be condensing into suns and planets, have hitherto shown evidences only of the presence of the first two of these elements, which, as is well known, make up a large part of the gaseous envelope of our planet, in the forms of air and aqueous vapour. With this he connected the hypothesis advanced by Grove, “that our atmosphere and ocean are but portions of the universal medium which, in an attenuated form, fills the interstellary spaces;[71] and further suggested as a legitimate and plausible speculation that these same nebulæ and their resulting worlds _may be evolved by a process of chemical condensation from this universal atmosphere_, to which they would sustain a relation somewhat analogous to that of clouds and rain to the aqueous vapour around us.” [Footnote 70: _American Journal of Science_, vol. xxiii. p. 124.]