64 THE SEVEN FOLLIES OF SCIENCE 



part of the road, it will, when the cause of stoppage is re- 

 moved, proceed on its journey by mere power of gravity. 

 Its path may be a circular road formed of the inclined 

 planes. But to avoid a circuitous route, a double road 

 ought to be made. The carriage not having a retrograde 

 motion on the inclined planes, a road to set out upon, and 

 another to return by, are indispensable." 



Fig. 16. 



How any one could ever imagine that such a contrivance 

 would ever continue in motion for even a short time, 

 except, perhaps, on the famous decensus averni, must be a 

 puzzle to every sane mechanic. I therefore give it as 

 a climax to the absurdities which have been proposed in 

 sober earnest. As a fitting close, however, to this chapter 

 of human folly, I give the following joke from the " Penny 

 Magazine," published by the Society for the Diffusion of 

 Useful Knowledge. 



" * Father, I have invented a perpetual motion ! ' said a 

 little fellow of eight years old. * It is thus : I would make 

 a great wheel, and fix it up like a water-wheel; at the top 

 I would hang a great weight, and at the bottom I would 

 hang a number of little weights; then the great weight 



