274 POPULAE HISTORY OP BIRDS. 
Yet stoop not, weary, to the welcome land. 
Though the dark night is near. 
" And soon that toil shall end ; 
Soon shalt thou find a summer home, and rest 
And scream among thy feUows; reeds shall bend. 
Soon, o'er thy shelter'd nest. 
" Thou'rt gone ! the abyss of heaven 
Hath swallowed up thy form ; yet, on my heart. 
Deeply hath sunk the lesson thou hast given. 
And shalt not soon depart. 
" He who, from zone to zone. 
Guides through the boundless sky thy certain flight. 
In the long way that I must tread alone, 
Will lead my steps aright." — William Cullen Bryant. 
On the islands and rocky coasts within the tropics^ fre- 
quented much by sea-fowl^ there are found great accumula- 
tions of their dung, somewhat altered and mixed with other 
matters : it forms a substance well known to the agricultu- 
rist as guano, and as forming his richest manure. A few 
years ago whole fleets of ships went to Ichaboe and other 
parts of the African coast, to procure supplies of this valu- 
able article. Mr. Darwin^ says that on the west coast of 
the intertropical parts of South America the beds are often 
several yards thick. "When analysed it is found to be com- 
^ Journal, p. 9, 
