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a rise in the water, they fill out the bladder, and this lightens the them. If the bladder breaks, the fish remains at the bot4 tom, and can only be held up by the most laborious exer
tion of the fins and tail. Accordingly, flat fish, as skaits and flounders, which have no air-bladders, seldom rise from the boitom, but are found lying on banks in the sea, or at the bottom of sea rivers.
The pressure and weight of the atmosphere, as shown by the barometer and air-pump, is near 15 pounds on every • square inch, so that if we could entirely squeeze out the air between our two hands, they would cling together with
a force equal to the pressure of double this weight, because 5 the air would press upon both hands; and, if we could contrive to suck or squeeze out the air between one hand and the wall, the hand would stick fast to the wall, being pressed on it with the weight of above two hundred weight, that is, near 15 pounds on every square inch of the hand. Now,
by a late most curious discovery of Sir Edward Home, ** the distinguished anatomist, it is found that this is the very
process by which flies, and other insects of a similar description, are enabled to walk up perpendicular surfaces,
however smooth, as the sides of walls and panes of glass 6 in windows; and io walk as easily along the ceiling of a room, with their bodies downwards and their feet over head. Their feet, when examined by a microscope, are found to have flat skins or flaps, like the feet of wch-footed animals, as ducks and geese; and they have towards the back part or heel, but inside the skin or flap, two very small toes, so connected with the slap as to draw it close down upon the glass or wall the fly walks on, and to squeeze out the air completely, so that there is a vacuum made between the
foot and the glass or wall. The consequence of this is, ry that the air presses the foot on the wall with a very considerable force, compared with the weight of the fly; for, if its feet are to its body in the same proportion as ours are to our bodies, since we could support by a single hand on the ceiling of the room, (provided it made a vacuum,) more than our whole weight, namely, a weight of fifteen stone, the fiy can easily move on four feet in the same manner, by help of the vacuum made under its feet. It has likewise been found that some of the larger sea animals are by the same construction, only upon a greater scale, enabled to climb the 8 perpendicular and smooth surfaces of the ice hills among which they live. Some kinds of lizard have the same. power of climbing, and of creeping with their bodies downwards along the ceiling of a room ; and the means by which they are enabled to do so are the same. In the large feet of thesc animals, the contrivance is easily observed, of the two toes or tightners, by which the skin of the foot is pinned down, and the air excluded in the act of walking or climbing ; but it is the very same, only upon a larger scale, with the mechanism of a fly's or a butterfly's foot; and both 9 operations, the climbing of the sea-horse on the ice, and
the creeping of the fly on the window or the ceiling, are performed exactly by the same power—the weight of the atmosphere—which causes the quicksilver to stand in the other weather-glass, the wind to whistle through a key-hole, and the piston to descend in a steam-engine.
The contrivance by which some creeper plants are enabled to climb walls, and fix themselves, deserves attentiot.
The Virginia creeper has a small tendril, ending in a claw, ** MR 10 each toe of which has a knob, thickly set with extremely
small bristles ; they grow into the invisible pores of the wall, and swelling, stick there as long as the plant grows, and prevent the branch from falling ; but when the plant dies, they become thin again, and drop out, so that the branch falls down. The Vanilla plant of the West Indies, climbs around trees likewise by means of tendrils; but when'it has fixed itself, the tendrils drop off, and leaves are formed.
Part II. i The Rein-deer inhabits a country covered with snow the
greater part of the year. Observe how admirably its hoof is formed for going over that cold and light substance, without sinking in it, or being frozen. The under side is covered entirely with hair, of a warm and close texture ; and the hoof, altogether, is very broad, acting exactly like the snowshoes which men have constructed, for giving them a larger space to stand on than their feet, and thus to avoid sinking. Moreover, the deer spreads the hoof as wide as possible
when it touches the ground; but, as this breadth would be 2 inconvenient in the air, by occasioning a greater resistance while he is moving along, no sooner does he lift the hoof, than the two parts into which it is cloven fall together, and so lessen the surface exposed to the air, just as we may recollect the birds doing with their bodies and wings. The shape and structure of the hoof is also well adapted to
scrape away the snow, and enable the animal to get at the · particular kind of moss (or lichen) on which he feeds.
This plant, unlike others, is in its full growth during the winter season; and the rein-deer, accordingly, thrives from 3 its abundance, notwithstanding the unfavorable effects of extreme cold upon the animal system. *.
There are some insects, of which the males have wings, and the females are grubs.or worms. Of these, the Glowwärm is the most remarkable : it is the female, and the male is a fly, which would be unable to find her out, creep
Ang as she does, in the dark lanes, but for the shining * light which she gives, to attract him.
There is a singular fish found in the Mediterranean, · called the Nautilus, from its skill in navigation. The back 4 of its shell resembles the hulk of a ship; on this it throws itself, and spreads a thin membrane to serve for a sail, paddling itself on with its feet as oars.
The Ostrich lays and hatches her eggs in the sands; her form being ill adapted to that process, she has a natural oven, furnished by the sand and the strong heat of the sun. The Cuckoo is known to build no nest for herself, but to lay in the nests of other birds ; but late observations show that she does not lay indiscriminately in the nest of all birds; she only chooses the nest of those which have bills 5 of the same kind with herself, and therefore, feed on the
same kind of food. The Duck, and other birds breeding in muddy places, have a peculiar formation of the bill : it is both made so as to act like a strainer, separating the finer from the grosser parts of the liquid, and it is more furnished with nerves near the point, than the bills of birds which feed on substances exposed to the light; so that it serves better to grope in the dark stream for food, being more sensitive. The bill of the Snipe is covered with a curious network of nerves for the same purpose ; but a bird, (the Toucan or Egg-sucker,) which chiefly seeds on the eggs found
6 in birds' nests, and in countries where these are very deep
and dark, has the most singular provision of this kind. Its bill is very broad and long: when examined, it is completely covered with branches of nerves in all directions ; so that, by groping in a deep and dark nest, it can feel its way as accurately as the finest and most delicate finger could. Almost all kinds of birds build their nests of materials found where they inhabit, or use the nests of other birds ; but the Swallow of Java lives in rocky caverns on the sea, where there are no materials at all for the purpose of building. 7 It is, therefore, so formed as to secrete in its body a kind
of slime, with which it makes a nest much prized as a delicate food in eastern countries.
Plants, in many remarkable instances, are provided for by equally wonderful and skillul contrivances. There is. one, the Fly-trap or Fly-catcher, which has small pric.les in the inside of two leaves, or half leaves, joined by à hinge; a juice or sirup is provided on their inner sûrface, and acts as a bait to allure flies There are several
small spines or prickles standing upright in this sirup, and 8 upon the only part of each leaf that is sensitive to the
touch. When the fly therefore, settles upon this part, its touching as it were the spring of the trap, occasions the leaves to shut and kill and squeeze the insect; so that its juices and the air arising from their rotting, serve as food to the plant.
In the West Indies, and other hot countries, where rain sometimes does not fall for a great length of time, a kind of plant called the Wild-pine, grows upon the branches of the trees, and also on the bark of the trunk. It has hol. 9 low or bag-like leaves, so formed as to make little reser
voirs of water; the rain falling into them through channels which close at the top when full, to prevent it from evaporating. The seed of this useful plant has small floating threads, by which, when carried through the air, it catches any tree in the way, and falls on it and grows. Wherever it takes root, though on the under side of a bough, it grows
straight upwards, otherwise the leaves would not hold water. · It holds in one leaf from a pint to a quart; and although it 10 must be of great use to the trees it grows on, to birds and other animals its use is even greater. Another tree, called Water-with, in Jamaica, bas similar uses: it is like a vine
in size and shape, but growing in very parched districts, is yet so full of clear sap or water, that on cutting a piece two or three yards long, and merely holding it to the mouth, a plentiful draught is obtained. In the East, there is a plant somewhat of the same kind, called the Brjuco, which grows near other trees and twines round them, with its end hanging downwards, but so full of juice, that on cutting it, a plentiful stream of water spouts from it; and this, not only by its touching the tree so closely must refresh it, but is a supply to animals, and to the weary herdsman on the mountains.
LESSON LXXXVI. From a Scene in Julius Cæsar.–SHAKSPEARE. * 1 Brutus.-What means this shouting? I do fear, the
Ay, do you fear it?
Brutus. I would not, Cassis ; yet I love him well :
Set honor in one eye, and death i'the other,
For, let the gods so speed me, as I love
Cassius. I know that virtue to be in you, Brutus,
In awe of such a thing as I myself.
We both have led as well; and we can both