12 Prof. Oliver Lodge on ' 



any kind of contact or physical connexion, it will be wise to 

 look carefully for the seat of the other component of the stress, 

 if there is one, and for the source of the energy concerned, 

 but I myself should feel extremely hazy as to their probable 

 locality. 



When action at a distance does present itself in Nature 

 (and if it ever does it is clearly going to be in connexion with 

 the operations of Life), it will be very well to overhaul our 

 axioms to see if they require modification. Till then I pro- 

 pose to state them in terms of the facts we know. This I will 

 attempt in another Part. 



Part III. 

 The Conservation of Energy and Universal Contact-action. 



The ground is now clear, I think, for a reply to Professor 

 MacGregor's criticism, as made in the Phil. Mag. (vol. xxxv. 

 p. 134) for February 1893 ; and incidentally I may hope to 

 answer or at least discuss the matter with some other critics, 

 notably Mr. Heaviside in his paper in the Phil. Trans. 1892. 



The first objection is that in my definition of energy I 

 assume the ordinary law of conservation, because I say, 

 in an early paper (Phil. Mag. Oct. 1879, viii. p. 278), "When- 

 ever work is done upon a body, an effect is produced in it 

 which is found to increase the working-power of that body 

 (by an amount not greater than the work done) ; hence this 

 effect is called energy, and it is measured by the quantity of 

 work done in producing it/' " The words ' is found/ " says 

 Dr. MacGregor, " indicate an appeal to experience/'' Most 

 true, so they do. My position is this : — Before making any 

 definition it is desirable and only civil to show the reasonable- 

 ness of it. To thrust a statement out without preamble or 

 explanation, under cover of the contention that being only a 

 definition or an enunciation one is at liberty to define or 

 enunciate as one pleases, is I fear a thing frequently done, but 

 it is barely polite, and it is apt to excite either resentment or 

 else undue and slavish submission. 



It is from no lack of love for Cambridge and the great men 

 she has nurtured that I venture to hold that the typically 

 Cambridge plan of text-book is liable to err in this direction. 

 An attitude of blind faith and mere assimilation is required 

 of a student for many of the earlier chapters, sometimes for 

 the whole of a book. The life, the interest, of the subject to 

 be treated, an exhibition of the reasonableness of the adopted 

 mode of treating it, are all neglected, and a ghastly skeleton 

 is presented to you bone by bone ; which truly is an admirable 

 structure when subsequently clothed in flesh by men of 

 sufficient genius, but which is liable to excite repulsion in a 



