8 SURVEYS OF NATURE. 



annually repair to the dreary lakes and defarts of Lapland, where 

 they perform the duties of incubation and nutrition in full fecu-- 

 rity, among lakes, rivers, fwannps, and mountains, covered with 

 thick and gloomy forefts. Here the ground remains moifl and 

 penetrable during the fummer ; here the woodcock, fnipe, and 

 flender billed birds feed at eafe; while the web-footed birds find 

 food in plenty from infinite fwarms of infects, From hence they 

 defcend at the approach of winter in numbers abfolutely in- 

 numerable; and which Linnaeus has obferved for eight whole 

 days and nights to cover the lurface of the river Calix, 



Jt has been often a fubjedt of aflonifhment, how thefe creatures 

 fhould perform fuch long journeys, fhould know whither to fteer; 

 and when to fet out. It is probable they rather follow the wea- 

 ther than the country ; and that they proceed as they continue 

 to find the atmofphere favourable, of the minuter variations of 

 which they are probably fpeedily fenfible and early apprized. 



Thus fome' birds by migrating inhabit every part of the earth ; 

 in general each climate has its peculiar birds. Thofe of the 

 temperate zone have little beauty of plumage, but the fmaller kinds 

 have exquifite melody of voice. Thofe of the torrid zone are of 

 bright and vivid colours, but of fcreaming voices, or are filent. 

 The frigid zones boafhlittle of either melody or brilliancy, but 

 abound with birds of the aquatic kinds, whole clothing is warm 

 not Ihewy, and fubftantial not gaudy. 



The number of quadrupeds little exceeds two hundred kinds: 

 of thefe, by grouping them together, we have obtained a tolerably 

 diftind: conception, having given to each that portion of atten- 

 tion which its Importance might claim: there is much greater 

 difficulty, in endeavouring to acquire equally determinate know- 

 ledge of birds, becaufe (i) their numbers are greater, probably 

 exceeding a thoufand, even omitting many varieties. (2) They are 

 fpread as well over the waters as the land. (3) Their changes 

 are greater in the courfe of their lives. (4) The difference be- 

 tween the fexcs is flronger. (5) The influence of climate is very 



con- 



