326 THE BIOLOGY OF THE SEASONS 



bodies are not, after all, doing very much. Perhaps the 

 mite is more of an agent than they ! It is expending 

 more energy relatively to its system, and it is not simply 

 going on in virtue of initial momentum. It is busy. The 

 heavenly bodies that do much in the way of giving off 

 energy, as our sun does, must some day rest. We have 

 only to look up to "yon dead world the moon" to see a 

 world at rest, though it is swept along unceasingly. 



Our thoughts also travel readily to the peculiar rest- 

 lessness of radium. Incessantly, and without appreciable 

 loss, the grain of radium pours forth heat and light. One 

 kind of radium ray is said to consist of little streams of 

 infinitesimally small corpuscles, which travel at the rate 

 of 100,000 miles a second. But after all, the radium 

 grain is being slowly used up ; it gives off a something 

 which is being turned into something else ; it finds a 

 relative rest in disintegrating. 



Let us linger still over the contrast of the lifeless and 

 the living. Throw a ball of potassium on the basin of 

 water, and it rushes about, fizzing and flaring like a thing 

 possessed, but in a minute all its marvellous activity is 

 over, its life as such is sped. But watch, by way of 

 contrast, the similar movements of the little whirligig 

 beetle on the pool ; it goes on for a while, like a little 

 water-sprite, darting here, there, and everywhere over the 

 surface, expending much energy. Unlike the potassium 

 pill, however, it does not go out for a long time at least. 

 When the gong to which it is adapted sounds, it ceases 

 to move, and begins to munch. It re-stokes its engine. 

 When it is tired, or when the external curfew to which 

 it is adapted tolls, it takes a rest. So it persists for weeks 

 and months, and, if it get big rests, it may be for years. In 

 fact, whether they be whirligig beetles or the trees of the 

 forest, living creatures are material systems which have 



