120 ANNUAL OF SCIENTIFIC DISCOVERY. 



years, deceiving ever with new expectations, which vanished upon nearer 

 approach, and finally reducing these dupes of hope to open insanity. The 

 phantom could not be grasped. It would be impossible to give a history of 

 these efforts, as the clearer heads, among whom the elder Droz must be 

 ranked, convinced themselves of the futility of their experiments, and were 

 naturally not inclined to speak much about them. Bewildered intellects, 

 however, proclaimed often enough that they had discovered the grand 

 secret ; and as the incorrectness of their proceedings was always speedily 

 manifest, the matter fell into bad repute, and the opinion strengthened 

 itself more and more that the problem was not capable of solution ; one dif- 

 ficulty after another was brought under the dominion of mathematical 

 mechanics, and finally a point was reached where it could be proved, that, 

 at least, by the use of pure mechanical forces, no perpetual motion could be 

 generated. 



We have here arrived at the idea of the driving force or power of a 

 machine, and shall have much to do with it in future. I must, therefore, 

 give an explanation of it. The idea of work is evidently transferred to 

 machines by comparing their arrangements with those of men and animals, 

 to replace which they were applied. We still reckon the work of steam 

 engines according to horse -power. The value of manual labor is determined 

 partly by the force which is expended in it (a strong laborer is valued more 

 highly than a weak one), partly, however, by the skill which is brought into 

 action. A machine, on the contrary, which executes work skilfully, can 



+> * ' 



always be multiplied to any extent ; hence its skill has not the high value 

 of human skill in domains where the latter cannot be supplied by machines. 

 Thus the idea of the quantity of work in the case of machines has been 

 limited to the consideration of the expenditure of force ; this was the more 

 important, as indeed most machines are constructed for the express purpose 

 of exceeding, by the magnitude of their effects, the powers of men and ani- 

 mals. Hence, in a mechanical sense, the idea of work is become identical 

 with that of the expenditure of force, and in this way I will apply it. 



How, then, can we measure this expenditure, and compare it in the case 

 of different machines ? 



I must here conduct you a portion of the way as short a portion as pos- 

 sible over the uninviting field of mathematico-mcchanical ideas, in order 

 to bring you to a point of view from which a more rewarding prospect will 

 open. And though the example which I shall here choose, namely, that of 

 a water-mill with iron hammer, appears to be tolerably romantic, still, alas, 

 I must leave the dark forest valley, the spark-emitting anvil, and the black 

 Cyclops wholly out of sight, and beg a moment's attention to the less poetic 

 side of the question, namely, the machinery. This is driven by a water- 

 wheel, which in its turn is set in motion by the falling water. The axle of 

 the water-wheel has at certain places small projections, thumbs, which, during 

 the rotation, lift the heavy hammer and permit it to fall again. The falling 

 hammer belabors the mass of metal, which is introduced beneath it. The 

 work therefore done by the machine consists, in this case, in the lifting of the 

 hammer, to do which the gravity of the latter must be overcome. The 



