Proceedings of the Polytechnic Association. 1077 



formed b}' the arms of a literary man with that effected by the arms 

 of a blacksmith of the same weight, would be preposterous, although 

 perhaps the literary man would outwalk the blacksmith. I have 

 myself walked nearly fifty miles in a day, but I should have found it 

 very difficult to propel myself that distance by my arms. The 

 second point is the fact that in walking we do a great deal of useless 

 work. Every time we take a step the center of gravity is raised 

 and then allowed to fall. Now, if man were a mere machine, this 

 falling of the center of gravity might be made to effect some work 

 which would tend to increase the final result. According to modern 

 theory, it might even be made to produce heat, but this heat would 

 unfortunately be useless for the production of muscular force. Let- 

 ting a man fall through ten feet will not restore the muscular 

 exhaustion produced by his raising himself through that space. 



Mr. Whitney. — It is true that in walking we raise the center of 

 gravity a little, but in the velocipede we raise one leg a great deal, 

 and the one balances the other. 



Mr. Blanchard. — Yes ; but one leg balances the other, and there is 

 thus no loss incurred. 



Dr. Yanderweyde.- — In the velocipede the weight of the body is 

 entirely supported, and every motion made by the feet is greatly 

 multiplied in the final result. It is nonsense to talk of the effect of 

 awkwardness in considering the mechanical results produced by any 

 machine. 



New Instrument fok CurriNG Glass. 



Mr. J. Johnson gave a very lucid explanation of a new instrument 

 made of steel, which he had just seen and used, and which cut glass 

 as well as the diamond. Unless some unforeseen objection should 

 arise, it promised to be of great utility. 



Street Sweeper. 



Mr. Adolphus Wurth exhibited a machine which he had invented 

 for sweeping the streets. It was similar in construction to machines 

 for this purpose which have been previously presented. 



Mr. Fisher. — The only true street cleaner is water. Sweeping 

 does little or no good. Wash your streets with water and blow the 

 water out of all lioles, and then you will have clean streets. Or, bet- 

 ter yet, have your streets so perfect th^t there shall be no holes in 

 them. 



