366 
BIRD-LIFE. 
Such immense assemblages of birds are far behind the 
most vivid conception of our imagination. They afford 
us, however, a safe explanation of the origin of the 
Guano Islands, which, at the present time, give rise to 
such an immense trade, and employment to so many 
people, as, indeed, they will continue to do for some time 
to come. The importance of birds in the case of these 
islands is proved by calculation: the early breeding 
places of certain Sea-birds have thus proved to be the 
richest source of revenue to a State. It is well known 
that guano is nothing else than a deposit, during centu¬ 
ries, on certain islands, of the excreta of Terns, Gulls, 
Scissor-billed Terns, Cormorants, Pelicans, and other 
Sea-fowl. At this very date, the yearly quantity collected 
of this valuable manure exceeds half a million of tons. 
44 This commerce, alone, demands a larger fleet of vessels 
than that which, in the previous century, carried on the 
communication of Spain with her colonies.” From this 
description it will be seen that the contemplation of such 
breeding colonies has other importance than being- 
regarded as a marvel of bird-life, showing the incredible 
numbers of birds breeding together in one place : in 
them we behold the rich source of the prosperity of 
entire nations, and can only thus thoroughly esteem and 
estimate their grandeur. 
