GRAVISTATIC HEAT 327 



heat than it was for Charles Lamb's Chinese to fashion 

 the fagots into a hut before starting the blaze for the 

 roasting of the pig. 



It is a customary thing in arguing for the doctrine of 

 the conservation of energy to cite the illustration of rais- 

 ing a dumb-bell and directly letting it drop to the ground, 

 and confining the attention to this simple case. It is ex- 

 plained, that in elevating the bell the lifter expends pre- 

 cisely the same number of units of muscular energy which 

 the bell will develop in thermal units on being let go and 

 striking the ground. "Muscular units expended, are 

 compensated by positional units gained, and positional 

 units lost, in their turn, are compensated by thermal 

 units gained; and so on." But suppose the bell is too 

 heavy for you to so much as budge? 



Ah, that is a question which you are supposed to be 

 polite enough never to ask. It seems as plain as can be 

 that when you lift the dumb-bell, you use up a certain 

 amount of muscular energy ; but it seems just as evident, 

 too, does it not, that when you pull and pull on an iron 

 stanchion, or try to lift a heavy rail, without effecting 

 the slightest movement in either, you are quite as cer- 

 tainly expending muscular energy? In the case of the 

 dumb-bell our good friends tell us these units of muscular 

 energy are replaced in the shape of kinetic energy by the 

 fall of the bell, thus balancing the dynamical ledger ; but 

 they do not volunteer as to how they are compensated in 

 the second instance. 



Doubtless you have seen a team of horses straining 

 to overcome a rise in the road and being lashed merci- 

 lessly by a brutal driver. Ten minutes pass, perhaps, 

 with no progress made, and the mired wheels stick fast. 

 Now, had all gone well and the horses succeeded without 

 delay or interruption in attaining the top of the hill, your 

 Conservationist would unctuously explain that the muscu- 

 lar energy expended by the animals is fully and accur- 

 ately compensated by the elevation of the load; but he 

 will have little if anything to say as to what becomes of 

 that same amount of energy where the load remains sta- 



