﻿Principles of Molecular Physics. 441 



Finally Professor Norton insists that, though the force of 

 gravity is not sensibly intercepted " this does not prove that a 

 tendency to interception does not exist : " and to prove the exist- 

 ence of this tendency he argues from " the supposition of a 

 wave-transmission of the force." To this I reply that nothing 

 proves the existence of the slightest tendency to the interception 

 of the action of gravity or any other action. Such an intercep- 

 tion can moreover be demonstrated to be absurd, as there is no 

 power in nature which is calculated to intercept action. As for 

 the " supposition " (the author seems here as elsewhere to accept 

 suppositions as proofs) I reply that it is only a supposition : 

 which moreover has nothing to do with the exertion of active 

 power; since the propagation of waves is a phenomenon of mo- 

 tion, not of its causality with which alone we are here concerned. 

 But my critic, who employs the indefinite word " force " instead 

 of " action," could not help confounding the exertion of power 

 with the consequent motion and its propagation. 



Out of fairness to Professor Norton, I must quote a short 

 passage that I find in one of his articles (Phil. Mag. vol. xxviii. 

 pp. 277, 278) where he gives his reason for admitting the inter- 

 ception of action. He says : 



" If two molecules are in equilibrium under their mutual actions, 

 the attractive and repulsive impulses exerted by each upon the 

 central atom of the other must be equal, and therefore no effective 

 action, either attractive or repulsive, can be transmitted to other 

 most distant particles on the same line. Under these circumstances, 

 one molecule in receiving the action of another, intercepts the action 

 that would otherwise take effect upon other most distant molecules. 

 This being admitted" &c. 



I recommend this curious reason to the consideration of phy- 

 sicists, of those especially who deal most with dynamics. As 

 for myself, I have italicized the word therefore, but shall not 

 stop now to give a special answer ; as the passage is not taken 

 from the paper to which I intended to reply. On the other 

 hand, the author must himself solve his argument in the case of 

 gravity, which, as he allows, is not sensibly intercepted. To 

 conclude. What I have said suffices, in my opinion, to show 

 that Professor Norton has been unsuccessful both in his an- 

 swers to my objections and in his arguments against some 

 of my conclusions. The cause of his ill-success lies almost 

 wholly in his too great facility to take a stand upon gratui- 

 tous hypotheses and mere conceptions, which he also con- 

 founds too frequently with " established truths." This fact is 

 now so evident that I might be allowed to consider his last 

 paper not as an answer to, but as a striking confirmation of, 

 my previous objections. 



