BY THE PEESIDENT. 55 



into a magnet for a time, so that it causes it to attract other bodies. 

 Force passing through all matter may therefore endow it with the 

 principle that we call gravitation. All experiments made to 

 explain the essence or cause of gravitation have failed, probably 

 because we cannot produce any gravitation vacuum, so to speak — 

 we cannot find any place where gravitation is not in which to 

 make the experiment. I need not detain you by speaking of the 

 other forms of force, as heat, light, electricity, magnetism, chemical 

 action, vital action. There are probably also some forms of force 

 derived from the sun, the nature of which we have not as yet even 

 conjectured. Whether animal and vegetable life is a combination 

 of the forms of force or a distinct force, we do not know ; but 

 whether we regard it as one or the other, we must look for it from 

 the sun. 



Comets have been hitherto regarded as mysterious and eccentric 

 bodies, but they are so numerous that T cannot help thinking that 

 they perform an important part in the plan of Nature. They do 

 not seem to obey the same laws as planets ; some comets are pro- 

 gressive and some retrograde, and when a comet appears for the 

 first time you can never predict where it will appear next. What 

 is a comet ? Sir John Herschel thinks that it must be material, 

 that is, have ponderable matter, because it reflects light which is 

 polarised. But if it is material it must have very little matter 

 in it. I have read that a man might carry the matter of a comet 

 in his hand. At least the star Sirius was visible through the tail of 

 a comet some thousands of miles thick, and comets have wandered 

 among the satellites of Jupiter, and the satellites gave the comets 

 the cut direct — they never moved out of their course in the least. 

 Now if the comet had any weight or material importance, the 

 moons of Jupiter must have taken some notice of it. I therefore 

 consider that some comets are scarcely if at all material, and if 

 there are any that cannot be classed under the term of ponderable 

 matter, they must be classed under the term of imponderable 

 matter or force. I should consider such comets therefore to be 

 some form of force ; and to represent the circulation of force 

 through space, sometimes going to the sun, sometimes from the 

 sun. I consider that, for the most part, this circulation of force 

 is quite invisible to us, and that it is only when it catches up and 

 carries with it some very, very thin nebulous matter, that it 

 becomes visible to us ; and we then call it a comet. I think that 

 comets are intimately connected with the circulation of force, 

 which circulation they may regulate and influence. It would be 

 an interesting study to investigate how far comets travel before 



