ll INTRODUCTION. 
that of commander or officer of a ship, whe- 
ther he please to make it a source of amuse- 
ment, or profit. 
In this, as well as in every other division of 
natural history, the knowledge requisite to dis- 
cover the scarce and rare varieties, can only be 
acquired by practice. To particularize objects 
that may present themselves to the traveller, is 
not the aim of this work; but, for the benefit 
of science, and his own interest, it is desirable 
to excite him to collect all he may meet with, 
until he has skill to select the most interesting: 
and I can assure him he will be amply remune- 
rated for his labor. I say all, for however com- 
mon they may appear in the countries he visits, 
they may be scaxce in England. 
SEVERAL years ago, I published a small 
pamphlet, entitled ‘‘ Directions to Captains of 
