240 SCIENTIFIC ILLUSTRATIONS [Nat 



Now if the mass of the earth had been greater or less, the force 

 of gravity would have been different ; in that case the strength 

 of fibre in the snow-drop, as it is, would have been too much or 

 too little ; the plant could not bow or raise its head at the right 

 time, fecundation could not take place, and its family would 

 have become extinct with the first individual that was planted, 

 because its " seed " would not have been " in itself," and there- 

 fore it could not reproduce itself. T. 



The Plan on -which Nature affords Assistance. 



There are two ways in which Nature affords aid : one is by 

 directly doing the particular thing required; the other is by 

 giving a creature the power to perform it himself. And as a 

 rule Nature refuses to do for a creature that which she has 

 endowed him with power to do for himself. In the Arctic 

 regions, where the cold of winter is intense, Nature has fur- 

 nished most animals with an efficient protection against its 

 influence. She has given its warm coat of fur to the bear, and 

 has provided the whale and walrus with a stratum of blubber, 

 whose non-conducting powers enable the animals to retain their 

 vital warmth in a medium which would seem to be inconsistent 

 with life. All animals, except man, in fact, are provided with 

 more or less covering to enable them to resist cold, and accord- 

 ingly we find that where they are naturally the inhabitants of 

 countries exposed to considerable varieties of temperature, they 

 appear to suffer very little inconvenience during the winter. 

 Not so man ; unprovided with any natural covering to shelter 

 him from the chilling influence of a wintry atmosphere, he 

 must have become to a certain extent a hybernating animal, 

 had not his reason and his industry supplied him with clothing 

 and fire to protect him from cold. Nature for this purpose was 

 content with bestowing on him the compensating faculty of 

 reason, leaving the rest to his own ingenuity and diligence. 



8. 



Nature's Marvellous Prevision. 



When a coral reef, says Chamisso, is of such a height as 

 to be almost wholly uncovered at low water, the zoophytes dis- 



