476 Transactions.^^Chemistru, 



Evidence of tliis sort, indeed, is to be had in every exliibition of these 

 movements of camphor, for whenever the camphor gets to the vessel's 

 side, it remains there motionless, whereas it should (according to the theory 

 we are examining) rebound therefrom, with great force. 



But apart from and independent of these results, it is, as I conceive, 

 very questionable whether any vapour emanating from a substance which is 

 of the same temperature as its environment, and in presence of air, has a 

 direct repellent effect thereon. However, this is a question of so general a 

 character that I cannot well extend the scope of this paper so far as to 

 take it into consideration now, but if you will allow me I will trench upon 

 it so much as to inform you of a few very interesting facts which are con- 

 nected with it, and also in an especial manner with the particular phenomena 

 we are considering. 



Experiments.' — Two pieces of camphor swung in air in close contiguity, 

 at the ends of very fine and long threads, do not manifest any repellent effect 

 in regard to each other, while, if placed upon water, though at first there is 

 an appearance of a mutually repellent force in action, there is, after a short 

 time has elapsed, an ajopearance of a mutually attractive force — they actually, 

 as you see, move toward each other and close together. Now, you wiU allow 

 that these results are not consistent with the theory which credits vapour 

 with direct repulsive effects. The case of turpentine is something similar 

 to the above. It is a substance which gives off vapour more freely 

 than camphor, yet when one sprinkles fine particles of cork upon it and 

 applies its vapour thereto, one cannot observe that the cork is at all 

 affected thereby. But not only this, one can get the very reverse of 

 repulsion during the emission of vapour ; thus, upon either turpentine or 

 kerosene a small piece of cork is placed, and a rod moistened with ammonia 

 is then brought to within about half an inch of it, v/hen the cork may 

 be observed to positively rush to the rod and follow it about as obediently 

 as a needle can respond to the movements of a magnet.''' 



Taken as a whole, the results which I have just described or exliibited 

 to you, do, as I conceive, indisputably show that this recession of particles 

 under the influence of camphor is, appearances notwithstanding, not due to 

 the direct impingement of vapour on them, but rather to some effect follow- 

 ing thereupon ; and it seems therefore necessarily to follow that the move- 

 ments of this substance (camphor) on water, are also not the direct result of 

 impingement, but the result of something which follows it. 



And now, with the popular theory thus disproved before you, it may 

 occur to some one here, as it did to me, that possibly these movements of 



* Volatile acids, also water, applied in this way have the reverse effect, while tur- 

 pentine is neutral. The rod alone, if warm, has also an apparent repulsive effect on 

 ■ the corlii. 



