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vocabulary of science as nothing less than a calamity . What is the reality 

 symbolized by these words, and where is it to be found 1 A simple illustra- 

 tion will serve both to indicate my objection to the use of the term potential 

 energy, and also to bring out my own view. Here are two stones, each of 

 them at the surface of the earth, weighing one pound. One of them I place 

 close to the edge of the mouth of a coal-pit, one hundred yards deep ; the 

 other I throw upwards, which, at its maximum height of one hundred feet, 

 is caught on the ledge of a rock. Now the theory of the conservation of 

 energy rec|uires us to believe that the latter stone has, by rising, acquired a 

 potential energy — a power of doing work of which the one remaining on the 

 groimd is altogether destitute. The stone resting on the rock can fall, while 

 — so says the theory — the stone on the edge of the pit cannot. Mr. Brooke 

 has referred to Dr. Joule's experiments. I will only say that in none of these 

 as explained to me by Dr. Joule himself, can I jBud am'thing opposed to the 

 positions I have been maintaining. The beautiful experiments by which he 

 determined the mechanical equivalent of heat, I am prepared to show, lend 

 no support whatever to the doctrine that the various forms of energy are 

 mutually convertible. In conclusion, I would, sir, thank Mr. Brooke for his 

 able criticism of my opinions as given in the paper this evening, and 

 elsewhere. Every intelligent and sincere objector I ever regard as a true 

 friend, both to myself and the great cause of truth. 



Rev. W. J. Irons, D.D. — I think the paper which has been read, and the 

 observations which have since been made upon it, are so important that 

 they need careful and minute consideration ; and a hasty discussion on a 

 subject of so much depth and importance would scarcely be becoming in a 

 scientific Society like this. For my ovm part, I feel strongly disposed to 

 acquiesce in the distioction which was drawn by the last speaker— namely, 

 that there is indeed a conservation of power, but not a conservation of 

 energy. I think that the conservation of power he refers to is almost iden- 

 tical with the doctrine of Albert and Thomas Aquinas concerning the impos- 

 sibility of either augmienting or diminishing the sum-total of the physical 

 universe — the impossibility, for instance, of annihilation, affirmed by Albert 

 the Great in very distinct terms. I made up my mind some years ago, when 

 I first considered the doctrine of the conservation of forces," that it meant 

 no more than had been understood under other terms in the middle ages ; 

 but probably at the present moment we are imable to decide what some gentle- 

 men ultimately mean when they lay down the law so positively about this 



conservation of forces.'' Is there no initiation of motion ? If Mr. Stuart 

 ^Nlill were here to-night, he might perhaps be able to teU us whether he 

 allows any such thing as a kind of initiation of action which is not a 

 deduction from previous forces in the universe. That would at once raise 

 the question whether materialism be the sum-total of the universe. I 

 should hope he would hardly go that length. Scepticism itself would assist 

 him there, as it would scarcely propound what would be almost a negation 

 of mental action itself. The whole subject is one which we are right 

 in considering with gravity. The philosophy of the subject has yet to 



