378 Mr. C. Brooke on the Dynamical Theory of Electricity . 



Lavoisier considered oxygen to be composed of a certain unknown 

 radical and of this principle, which he materialized under the 

 name caloric. This point of view I shall develope in a follow- 

 ing chapter. 



In direct combinations the motion is destroyed and converted 

 into heat : just as a finite velocity can only be imparted to a 

 body in a finite time, so combination will always require for its 

 production a greater or less time, but always a definite one. 



As the phenomena of indirect combination (or that produced 

 by the nascent state) require (1) a solution, (2) an absorption of 

 heat or a cooling, the time necessary for their development will 

 be greater (1) as the solubility of the substances acting in the 

 menstrua is smaller, (2) as the absorption of heat is greater. 



The action of time need not be mysterious ; we must always 

 either explain it simply, or wait for facts to account for it. 



L. On the Dynamical Theory of Electricity. 

 By C. Brooke, F.R.S. 



To Professor Tyndall, F.R.S. 



16 Fitzroy Square, W. 

 My dear Sir, October 13, 1866. 



I HAVE lately been led, in relation to a new edition of my 

 ' Elements of Natural Philosophy ' now in the press, to re- 

 consider the whole question of electricity, and I have become 

 strongly impressed with the reality of the dynamical theory. I 

 have hence naturally been induced to look about for confirmatory 

 facts ; and a strong, and (to the best of my knowledge and belief) 

 a new fact has presented itself to me. It has long been known 

 that if a bar of antimony and one of bismuth be connected, and 

 a current be transmitted from antimony to bismuth, heat will be 

 developed at the point of junction ; and, on the contrary, if the 

 current pass from bismuth to antimony, cold will be produced. 

 Now it struck me that if in the former, as in all other cases in 

 which heat is developed in the passage of a current, a portion of 

 electric potential is (as I believe) converted into thermic potential, 

 or heat, there ought in the latter case to be an inductive conversion 

 of thermic into electric potential ; and if so, there should be a loss 

 of current in the first instance, and a gain in the second : and 

 such appears to be the fact. On duly balancing the thermo- 

 element above mentioned in a Wheatstone's bridge, the deflec- 

 tion of the needle followed the direction of the current, and the 

 anticipated loss or gain of current was fully realized. If you can 

 find room for this notice in the Philosophical Magazine, you will 

 greatly oblige, y ours faithfully, 



Charles Brooke. 



