XIV 
INTRODUCTION. 
or Aurora Borealis, attract the eyes of all their attendant foes. 
Other kind of fiflies, in duller garbs, keep alfo together in bo- 
dies, but change their movements as may bell: fuit their differ- 
ent modes of attack or defence, in preying upon, or efcaping from 
each other as they pafs along. * All thefe various tribes of fiflies, 
but particularly that of the Herring, are in their turns encoun- 
tered and preyed upon by the whole hofts of fea-fowl, which 
continually watch all their motions. Some are feen to hover 
over the fhoals. of fiflies, and to wheel about in quick and glancing 
evolutions, and then to dart down like a falling plummet upon 
the feledled objedt, which is gliding near the furface of the wa- 
ter, and inftantly to rife, and devour the living victim on the 
wing. Others, equally, alert and rapid in their purfuit, plunge 
and dive after their prey to greater depths ; while the lefs adlive 
birds fcem content to devour only fuch of the fiflies as have been 
killed or wounded, and caff out on the flanks, or left in the rear 
of the main body. 
In this great, this wonderful emigration of birds and fiflies, 
it is evident that they are amply provided on their way with an 
abundance of food, which they derive from each other ; and that 
the flioals of fiflies which the fea-fowl attend, are impelled fouth- 
* “ Fishes are the most voracious animals in nature. Many species 
prey indiscriminately on every thing digestible that comes in their way, 
and devour not only other species of fishes, but even their own. As a 
counterbalance to this voracity they are amazingly prolific. Some 
bring forth their young alive ; others produce eggs. The viviparous 
Blenny brings forth 200 or 300 live fishes at a time. Those which pro- 
duce eggs are all much more prolific, and seem to proportion their stock 
to the danger of consumption. Lewenhock affirms that the Cod 
spawns above nine millions in a season. The Flounder produces above 
one million, and the Mackarel above 500,000. Scarcely one in a hun- 
dred of these eggs, however, Is supposed to come to maturity : but two 
wise purposes are answered by this amazing Increase ; It preserves the 
species in the midst of numberless enemies, and serves to furnish the 
rest with a sustenance adapted to their nature.” — EncycL Britan, 
