SCIENCE 



another, but how can a mechanical force act upon 

 itself? How can a body fall unless there is some 

 other body for it to fall to? The earth falls toward 

 the sun, but never gets there; the sun falls toward 

 some other greater sun, and that toward some other 

 centre of forces, but what can the whole universe 

 fall toward? Is it not like asking, Will the puppy 

 ever overtake his own tail? The self -activity of the 

 universe seems to me as impossible as any perpetual 

 motion machine ever dreamed of. Power moves 

 down an incline of temperature or gravity or a 

 gradient of some sort. There must be inequality 

 and fixed points. The inertia of the gun resists the 

 explosive power of the powder and hurls the ball; 

 the resistance of the ground enables us to walk. 

 Power is available to power. To avail ourselves of 

 gravity we must first overcome it. We must lift the 

 lever up before we can ask gravity to pull it down. 

 We have to pit gravity against gravity. 



The low uniform temperature of the ocean holds 

 enough potential power to drive all the ships on its 

 surface, and more, if we could only bring it to bear 

 create an incline down which it could flow. But 

 this would require an equal power. Then there is an 

 incline of temperature from the southern oceans to 

 the northern that causes the great ocean currents, 

 but their power is not available, because there are 

 no stable shores to their rivers upon which to plant 

 our machinery. 



265 



