STORM PETRELS. 423 



ance,) they inhabit the whole range of the ocean ; different 

 latitudes having their respective tenants, whether on the 

 north or south side of the line ; but, though they breed in 

 various latitudes, they may all be said to have a tendency 

 to move polarly as the season of incubation approaches. 

 At this point there is a motion of the water, especially 

 of the surface water, towards the equatorial regions, as 

 is proved by the drifting of icebergs, and may be rea- 

 sonably explained by the melting of the snow and ice, 

 which, during the winter, are piled high, both on the 

 surface of the land and on that of the frozen sea. On 

 tlie latter, the hummocks are indeed much more elevated 

 than those who have not considered the subject would be apt 

 to suppose ; for when the ice has acquired considerable 

 thickness, in the early part of the season, and before the 

 tranquillity of the polar winter sets in, it is often shattered 

 by the roll of the waters, and the boards, turned on edge, are 

 driven against each other, where they not only stand high, 

 but retain the snow which drives over the more level parts. 

 The casualties which happen to life at that season are con- 

 siderable, and many of the remains are preserved in the snow 

 and ice, both at sea and on the land. These are loosened 

 by the heat in spring ; and the land portion is, in a great 

 measure, brought down by the " freshes ;" so that the sea 

 becomes the common receptacle of the whole. The fatty 

 part of these remains, especially, floats southward with the 

 surface water, and meets the Pelagic birds as they collect 

 northward to their breeding places. Nor is the fatty or oily 

 matter the only food for birds which then floats with the 

 motion of the sea ; for the fulmars, the gulls, and a variety 

 of other birds all the scavengers of the sea, indeed then 

 find an abundance ; and as the supply continues all the time 

 that the ice and snow are melting, which is nearly till they 

 again begin to freeze, the birds find a continued supply for 



