1^56.] Prof, Tyndall, on tluB Duposition of Force. 159 



physical radiation taking place between the metals, it would afford a 

 reason for the effects produced in Volta's contact experiment, with- 

 out supposing a force without consumption or change in the matter 

 evolving it. This led him to try the effect of closely approximating 

 discs of zinc and copper without bringing them into metallic contact ; 

 and it was found that discs thus approximated, and then quickly 

 separated, affected the electroscope just as though they had been 

 brought into contact. Without giving any opinion as to what may 

 be the nature of the radiation in Moser*s phenomena, this experi- 

 ment removes the difficulty presented by that of Volta to the 

 chemical theory of electricity. 



The general scope of the argument from the negation of per- 

 petual motion leads the mind to regard the so-called imponderables 

 as modes of motion, and not as different kinds or species of matter ; 

 the recent progress of science is continually tending to get rid of the 

 hypotheses of fluids, of occult qualities, or latent entities, which 

 might have been necessary in an earlier stage of scientific enquiry, 

 and from which it is now extremely difficult to emancipate the 

 mind : but if we can, as it is to be hoped we shall, ultimately arrive 

 at a general dynamic theory, by which the known laws of motion 

 of masses can be applied to molecules, or the minute structural 

 parts of matter, it seems scarcely conceivable that the mind of 

 man can further simplify the means of comprehending natural 

 phenomena. 



[W. R. G.] 



WEEKLY EVENING MEETING, 



Friday, February 1. 



The Duke op Northumberland, K.G. F.R.S. President, 

 in the Chair. 



Pbofessor Tyndall, F.R.S. 



On the Disposition of Force in Paramagnetic and 

 Diamagnetic Bodies, 



The notion of an attractive force, which draws bodies towards the 

 centre of the earth, was entertained by Anaxagoras and his pupils, 

 by Democritus, Pythagoras, and Epicurus ; and the conjectures 

 of these ancients were renewed by Galileo, Huyghens, and others, 

 who stated that bodies attract each other as a magnet attracts iron. 

 Vol. II. M 



