AND AMERICAN RURAL SPORTS. 
9 
weaker, so are these furnished with the most admirable 
powers of evading their destroyers. In the economy of 
insects, we constantly observe, that the means of defence, 
not only of the individual creatures, but of their larvae and 
pupae, against the attacks of other insects, and of birds, is 
proportioned, in the ingenuity of their arrangements, to 
the weakness of the insect employing them. Those species 
which multiply the quickest have the greatest number of 
enemies. Bradley, an English naturalist, has calculated 
that two sparrows carry, in the course of a week, above 
three thousand caterpillars to the young in their nests. 
But though this is, probably, much beyond the truth, it is 
certain that there is a great and constant destruction of 
individuals going forward; and yet the species is never 
destroyed. In this way a balance is kept up, by which 
one portion of animated nature cannot usurp the means of 
life and enjoyment which the world offers to another 
portion. In all matters relating to reproduction, Nature is 
prodigal in her arrangements. Insects have more stages to 
pass through before they attain their perfect growth than 
other creatures. The continuation of the species is, there- 
fore, in many cases, provided for by a much larger number 
of eggs being deposited than ever become fertile. How 
many larvae are produced, in comparison with the number 
which pass into the pupa state; and how many pupae perish 
before they become perfect insects! Every garden is 
covered with caterpillars; and yet how few moths and 
butterflies, comparatively, are seen, even in the most 
sunny season. Insects which lay few eggs are, commonly, 
most remarkable in their contrivances for their preserva- 
tion. The dangers to which insect life is exposed are 
manifold; and therefore are the contrivances for its preser- 
vation of the most perfect kind, and invariably adapted 
to the peculiar habits of each tribe. The same wisdom 
determines the food of every species of insect; and thus 
some are found to delight in the rose-tree, and some in the 
oak. Had it been otherwise, the balance of vegetable life 
would not have been preserved. It is for this reason that 
the contrivances which an insect employs for obtaining 
its food are curious, in proportion to the natural difficulties 
of its structure. The Ant-lion is carnivorous, but he has 
not the quickness of the spider, nor can he spread a net 
over a large surface, and issue from his citadel to seize a 
victim which he has caught in his out works. He is 
therefore taught to dig a trap, where he sits, like the 
unwieldy giants of fable, waiting for some feeble one to 
cross his path. How laborious and patient are his opera- 
tions — how uncertain the chances of success! Yet he never 
shrinks from them, because his instinct tells him that by 
these contrivances alone can he preserve his own existence, 
and continue that of his species. — Lib. Ent. Knowledge. 
C 
BASIN OF THE MISSISSIPPI, 
IN A GEOLOGICAL VIEW. 
The hydrographical basin of the Mississippi displays, 
on the grandest scale, the action of running water on the 
surface of a vast continent. This magnificent river rises 
nearly in the forty-ninth parallel of north latitude, and 
flows to the Gulf of Mexico in the twenty-ninth — a course, 
including its meanders, of nearly five thousand miles. It 
passes from a cold arctic climate, traverses the temperate 
regions, and discharges its waters into the sea, in the region 
of the olive, the fig, and the sugar-cane. * No river affords 
a more striking illustration of the law before mentioned, 
that an augmentation of volume does not occasion a propor- 
tional increase of surface, nay, is even sometimes attended 
with a narrowing of the channel. The Mississippi is a 
mile and a half wide at its junction with the Missouri, 
the latter being half a mile wide; yet the united waters 
have only, from their confluence to the mouth of the Ohio, 
a medial width of about three quarters of a mile. The 
junction of the Ohio seems also to produce no increase, but 
rather a decrease of surface.! The St. Francis, White, 
Arkansas, and Red rivers, are also absorbed by the main 
stream with scarcely any apparent increase of its width; 
and, on arriving near the sea at New Orleans, it is some- 
what less than half a mile wide. Its depth there is very 
variable, the greatest at high water being one hundred and 
sixty-eight feet. The mean rate at which the whole body 
of water flows, is variously estimated. According to 
some, it does not exceed one mile an hour. X The alluvial 
plain of this great river is bounded on the east and west 
by great ranges of mountains stretching along their respec- 
tive oceans. Below the junction of the Ohio, the plain is 
from thirty to fifty miles broad, and after that point it goes 
on increasing in width till the expanse is perhaps three 
times as great! On the borders of this vast alluvial tract 
are perpendicular cliffs, or “ bluffs,” as they are called, 
composed of limestone and other rocks. For a great dis- 
tance the Mississippi washes the eastern “bluffs;” and 
below the mouth of the Ohio, never once comes in contact 
with the western. The waters are thrown to the eastern 
side, because all the large tributary rivers enter from the 
west, and have filled that side of the great valley with a 
sloping mass of clay and sand. For this reason, the eastern 
bluffs are continually undermined, and the Mississippi is 
slowly but incessantly progressing eastward. § 
The river traverses the plain in a meandering course, 
describing immense and uniform curves. After sweeping 
* Flint’s Geography, vol. i. p. 21. f Ibid. p. 140. | Darby. 
§ Geograph. Descrip, of the State of Louisiana, by W. Darby, Philadelphia, 
1816. p. 102. 
