Mr. Addams on the Repulsive Action of Heat. 415 



rections and extensions of the theory of electro-chemical de- 

 composition, given in the Fifth and Seventh Series of these 

 Researches. The expressions I would now alter are those 

 which relate to the independence of the evolved elements of 

 the poles or electrodes, and the reference of their evolution to 

 powers entirely internal (524. 537. 661. )• The present paper 

 fully shows my present views; and I would refer to para- 

 graphs 891. 904. 910. 917. 918. 947. 963. 1007. 1031. &c., as 

 stating what they are. I hope this note will be considered as 

 sufficient in the way of correction at present; for I would 

 rather defer revising the whole theory of electro-chemical de- 

 composition until I can obtain clearer views of the way in 

 which the power under consideration can appear at one time 

 as associated with particles giving them their chemical attrac- 

 tion, and at another as free electricity (493. 957.)' — M. F. 

 Royal Institution, March 31, 1834. 



LXV. Notice of some Experiments "uohich show a repulsive Ac» 

 lion between heated Surfaces and certain pulverulent Bodies. 

 By R. Addams, Esq., Lecturer on Chemistry and Natural 

 Philosophy*. 



T^HAT caloric possesses a repellent force is assumed from 

 -*- the effects it produces upon matter in general : but there 

 are those who do not allow that we have any unequivocal 

 evidence of calorific repulsion between independent bodies, 

 such, for example, as two separate masses of heated iron ; in- 

 deed, the question whether caloric does not act repulsively 

 at sensible distances, has recently been made the subject of 

 experimental investigation by the Rev. Professor Powellf, 

 who, in the Philosophical Transactions for the last year, 

 has given an account of an elegant and refined mode of 

 testing the repulsion between two heated lenticular masses of 

 glass. 



The following description of some experiments which seem 

 to bear upon the question may not, therefore, be unacceptable 

 to those who are interested in this branch of inquiry. 



Exp. 1. A small quantity of silica (prepared by precipitation 

 from its alkaline solution) was heated upon a platinum cap- 

 sule : when the heat — that from a spirit-lamp — had acted 

 for a second or two, the powder moved, by the least mo- 

 tion of the capsule, as if it were floating upon a liquid, 

 having a mobility almost equal to that of mercury. The fric- 



* Communicated by the Author. 



t Lond. and Edinb. Phil. Mag., vol. vi. p. 58. 



