76 WATER-RAT. 



The eagle-owl,* could it be proved to belong to us, is so 

 majestic a bird, that it would grace our fauna much. I never 

 was informed before where wild geese are known to breed. 



You admit, I find, that I have proved your fen salicaria to 

 be the lesser reed-sparrow of Ray ; and I think you may be 

 secure that I am right ; for I took very particular pains to 

 clear up that matter, and had some fair specimens ; but, as 

 they were not well preserved, they are decayed already. You 

 will, no doubt, insert it in its proper place in your next edition. 

 Your additional plates will much improve your work. 



De Buffon, I know, has described the water shrew-mouse ;f 

 but still I am pleased to find you have discovered it in Lincoln- 



The back becomes white within eight days. During the whole of this 

 remarkable change in the fur, no hair falls from the animal. Hence it 

 appears, that the hair actually changes its colour, and that there is no 

 renewal of it. The fur continues white till the month of March, or even 

 later, depending on the temperature of the atmosphere, and, by the 

 middle of May, it has again assumed its gray colour. But the spring 

 change is different from the winter, as the hair is completely shed. 



An instance of a similar change may be instanced in the ptarmigan, 

 (tetrao lagopus. ) Its summer plumage is ash gray, mottled with dusky 

 spots and bars. At the approach of winter, the dark colours disappear, 

 and its feathers are then found to be pure white. We are naturally led 

 to inquire what benefit the animals receive from this periodical change, 

 as we know that the All-wise does nothing in vain. Colour has a great 

 influence on the ratio at which bodies cool. It is an established law, that 

 surfaces which reflect heat most readily, allow it to escape very slowly by 

 radiation. White objects reflect most readily, consequently there will be 

 a proportionate difficulty in its radiation of heat. If a black animal and 

 a white one were placed in a higher temperature than that of their own 

 body, the heat will enter the black one with the greatest rapidity, and 

 soon elevate its temperature considerably above that of the other. These 

 differences manifest themselves in wearing black and white coloured 

 clothing during hot weather ; so that if these animals are placed in a 

 temperature considerably lower than their own, the animal which is black 

 will give out its heat by radiation to the surrounding objects sooner than 

 itself, by which its temperature will speedily be reduced, while the white 

 animal will part with its heat by radiation at a much slower rate. Hence 

 it would appear that the clothing of animals is suited in colour to the 

 temperature of the situations where they localize. Accidental variations, 

 however, sometimes occur, as in some birds we have already mentioned at 

 page 36. A black hare was shot at Combe, near Coventry, in February, 

 1828 ; and another was killed at Netley, Shropshire, by the Rev. F. W. 

 Hope. ED. 



* The strix bubo has been killed in Yorkshire, Sussex, and Scotland, 

 It is a native of Norway and other parts of Europe. ED. 



f- This quadruped has been found in many parts of Great Britain : it 

 seems to have been long overlooked in this country. In Turton's British 

 Fauna } there is a second species of water shrew mentioned by the name, 



