is not necessitated by the so-called “stoichiometric laws”; but, on the other hand, a molecular constitution of matter seems to be demanded by the phenomenon known as the “Brownian Movement,” _i.e._, the spontaneous, irregular and apparently perpetual movement of microscopic portions of solid matter when immersed in a liquid medium; such movement appearing to be explicable only as the result of the motion of the molecules of which the liquid in question is built up.[100] [98] For a critical examination of Materialism, the reader is referred to the present writer’s _Matter, Spirit and the Cosmos_ (Rider, 1910), especially Chapters I. and IV. [99] W. OSTWALD: “Faraday Lecture,” _Journal of the Chemical Society_, vol. lxxxv. (1904), pp. 506 _et seq._ See also W. OSTWALD: _The Fundamental Principles of Chemistry_ (translated by H. W. Morse, 1909), especially Chapters VI., VII. and VIII. [100] For an account of this singular phenomenon, see Prof. JEAN PERRIN: _Brownian Movement and Molecular Reality_ (translated from the _Annales de Chimie et de Physique_, 8me Séries, September, 1909, by F. Soddy, M.A., F.R.S., 1910). CHAPTER VII MODERN ALCHEMY “Modern Alchemy.” § =85.= Correctly speaking, there is no such thing as “Modern Alchemy”; not that Mysticism is dead, or that men no longer seek to apply the principles of Mysticism to phenomena on the physical plane, but they do so after another manner from that of the alchemists. A new science, however, is born amongst us, closely related on the one hand to Chemistry, on the other to Physics, but dealing with changes more profound and reactions more deeply seated than are dealt with by either of these; a science as yet without a name, unless it be the not altogether satisfactory one of “Radioactivity.” It is this science, or, perhaps we should say, a certain aspect of it, to which we refer (it may be fantastically) by the expression “Modern Alchemy”: the aptness of the title we hope to make plain in the course of the present chapter. X-rays and Becquerel rays.