ABSTRACT OF PROCEEDINGS. XX111. 



Democritus, Epicurus, Lucretius, Aristotle, Gassendi, 

 Descartes, Boyle, Hooke, Newton, Helmholtz, and others 

 in the evolution of the theory. The evidence of the exist- 

 ence of various orders of atoms was then indicated, viz., 

 of the mechanical atom, the chemical molecule and atom, 

 the aetherergic molecule and atom, the atomic molecule 

 and atom, electron, or corpuscle. The significance of con- 

 stitutional formulae in chemistry and of stereochemical 

 knowledge, in relation to the progress of science and 

 industry was briefly outlined, and the fact dwelt upon that 

 the extension of human power is dependent upon abstract 

 scientific knowledge. The aids to research, by means of 

 which sense-limitations were transcended, were illustrated 

 by a large number of experiments, and it was demonstrated 

 in what way the structure of matter is being daily more 

 and more completely and exactly determined by physical 

 investigators. The lecture was given in the Physics 

 Lecture Theatre in order that the experimental illustration 

 of the lecture might be possible. The experimental demon- 

 strations included the behaviour of electrons in the magnetic 

 field, and illustrated the development of knowledge of 

 matter through Sir Wm. Orookes' researches, and the 

 modern developments of the electron theory. Various 

 orders of luminescence, fluorescence, and the radiations of 

 Lenard, Rbntgen, Becquerel, etc., and of the radioactive 

 substances were indicated and shewn. 



