190 THE REIGN OF LAW. 



actly with the lichens of the mountain peaks, give 

 place in winter to the pure white which matches 

 not less perfectly with the wreaths of snow. 



This is indeed a change which requires for its 

 production the agency of other laws than those 

 merely of reflected light, because the substitution 

 of one entire set of feathers for another of a dif- 

 ferent colour, twice in every year, implies arrange- 

 ments which lie deep in the organic chemistry of 

 the bird. The various genera of Sand-Grouse and 

 Sand-Partridges, which frequent the deserts and 

 naked plains of the Asiatic continent, are coloured 

 in exquisite harmony with the ground. Our com- 

 mon Woodcock is another excellent example, and 

 is all the more remarkable as there is one very 

 peculiar colour introduced into the plumage of 

 this bird which exactly corresponds with a parti- 

 cular stage in the decay of fallen leaves — I mean 

 that in which the browns and yellows of the 

 Autumn rot away into the pale ashy skeletons 

 which lie in thousands under every wood in winter. 

 This colour is exactly reproduced in the feathers 

 of the Woodcock, and so mingled with the dark 

 browns and w 7 arm yellows of fresher leaves, that 



