Birds inhabiting the Southern Ocean. 289 



wrecked they lit a fire upon the rocks, when, to their astonish- 

 meut, a large quantity of Stormy Petrels flew into it, and others 

 dashed themselves against the rocks on which the fire was 

 lighted, although these birds were rarely seen in the daytime. 

 This shows that these birds are nocturnal in their habits when 

 near land ; at sea, however, they are much more common in the 

 daytime than at night j and I have never heard of one of them, 

 or any other Petrel, flying into a ship's port with a light in it, 

 although this is by no means uncommon with flying-fish. 



The extraordinary number of ocean-birds found in the cold 

 regions of the earth, in comparison with the small number found 

 in the tropics, is a very remarkable fact, as it is exactly the reverse 

 of what we see on land. It can, however, I think, be accounted 

 for as follows : — The higher plants have to deoxidize large quan- 

 tities of water and carbonic acid, for the formation of the sugar, 

 various kinds of oil, camphor, resin, &c., that they secrete ; but 

 this process absorbs an equally large amount of heat and light, 

 which can only be supplied by the sun, consequently they must 

 inhabit warm or temperate climates, and live on land, or, at any 

 rate, must have the greater portion of their leaves exposed di- 

 rectly to the air ; for water is such a powerful absorbent of heat- 

 rays, that a depth of a few inches only is enough to prevent 

 nearly all those that reach the earth on a cloudless day from 

 penetrating further. The lower plants, however, which have 

 little to develope but cellulose and chlorophyll, require less 

 light, and but little heat ; they are thus enabled to live under 

 water, and in regions where the more highly organized forms 

 would die, and, being unopposed, they increase here in number 

 and dimensions far more than in warmer latitudes or on land. 

 Now, as water maintains a more equable temperature than land, 

 it follows that in cold regions the sea supports nearly the whole 

 of the vegetation. This entails an equally large population of 

 the lower marine animals, which subsist on the vegetation, and in 

 their turn supply food to the Petrels, which, carrying about 

 with them in their lungs an apparatus for producing heat, are 

 not under the same necessity as the higher plants of living only 

 in warm climates; but, as the heat in summer is much less in 

 the southern hemisphere than in equal latitudes in the northern, 



N. S. VOL, I. X 



