1125. Why can gossamer spiders float through the air?

Because, having no wings, and being deficient in the active muscular powers of other spiders, they have been endowed with the power of spinning a web which is so light that it floats in the air, and bears the body of the gossamer spider from place to place. Each web acts as a balloon, and the spider attached thereto is a little aeronaut.1126. Why do crickets make a peculiar chirping sound?

Because they have hard wing cases, by the friction of the edges of which they cause their peculiar noise, to make known to each other where they are, in the dark crevices in which they hide.

1127. Why has the glow-worm a brush attached to its tail?

Because it is necessary to keep its back very clean, that the light which its body emits may not be dimmed.1128. Why does the glow-worm emit a light?

Because the female glow-worm is without wings, but the male is a winged insect. The female, therefore, is endowed with the power of displaying a phosphorescent light. The light is only visible by night, but it is, nevertheless, beautifully adapted for the purpose stated, because the male is a night-flying insect, and never ventures abroad by day.

"They that go down to the sea in great ships, that do business in great waters these see the works of the Lord, and his wonders in the deep."—Psalm cvii.

There exists some difference of opinion between naturalists upon the uses of the light of a glow-worm; there are some who doubt that it is exhibited to attract the flying insect. The objectors, however, offer no explanation of the luminous properties of the worm. Sir Charles Bell says the preponderance of the argument is decidedly in favour of the explanation we have given.1129. Why does not the iris of the fish's eye contract?

Because the diminished light in water is never too strong for the retina.1130. Why is the eye of the eel covered with a transparent horny covering?

Because, as the eel lives in holes, and pushes its head into mud, and under stones, &c., it needed such a covering to defend the eye.1131. Why is the whale provided with an eye, having remarkably thick and strong coats?

Because, when he is attacked by the sword-fish and the shark, he is almost helpless against his enemies, as they fix themselves upon his huge carcase. He therefore dives with them down to a depth where the pressure of the water is so great that they cannot bear it. The eye of the whale is expressly organised to bear the immense pressure of extreme ocean depths, without impairing the sight.1132. Why have fishes no eyelids?

Because the water in which they swim keeps their eyes moist. Eyelids would therefore be useless to them.1133. Why have fishes the power of giving their eye-balls very sudden motion?

Because, having no eyelids (such organs being unnecessary to keep their eyes moist), they still need the power of freeing their eyes from the contact of foreign matters; and this is secured to them by the power they have of giving the eyeball a very rapid motion, which causes reaction in the fluid surrounding it, and sweeps the surface.

This motion may frequently be seen in the eyes of fishes, in glass globes.

"And God made the beast of the earth after his kind, and cattle after their kind, and everything that creepeth upon the earth after his kind: and God saw that it was good."—Genesis i.

1134. Why is the lachrymal secretion of the horse's eye thick and glutinous?

Because, as his eye is large, and constantly exposed to dust on journeys, it is provided with a viscid secretion, which cleanses the eye, and more instantly and securely removes the dust, than a watery secretion would.1135. Why does the lower bill of the sea-crow project beyond the upper one?

Because the bird obtains his food by skimming along the water, into which he dips his bill, and lifts his food out.1136. Why do the mandibles of the cross-bill overlap each other?

Because the bird requires a peculiar bill, to enable it to split seeds into halves, and to tear the open cones of the fir-tree.1137. Why are the tails of fishes so much larger than their fins?

Because their tails are their chief instruments of motion, while their fins are employed simply to direct their progress, and steady their movements.1138. Why have oxen, and other quadrupeds a tough ligament called the "pax-wax," running from their backs to their heads?

Because their heads are of considerable weight; and having frequent occasion to lift them, they are provided with an elastic ligament, which is fastened at the middle of their backs, while its other extremity is attached to the head. This enables them to raise their heads easily; otherwise the effort to do so would be a work of great labour. To the horse, the pax-wax acts as a natural bearing-rein, assisting it to hold its head in that position which adds to the grace and beauty of the animal.

In carving beef, this ligament may be seen passing along the vertebrÆ of the neck, the chuck, and the fore ribs.

"He shall feed his flock like a shepherd; he shall gather the lambs with his arm, and carry them in his bosom, and shall gently lead those that are with young."—Isaiah xl.

1139. Why have the females of the kangaroo and opossum tribes pouches, or pockets, formed in the skin of their breasts for the reception of their young?

Because their young ones are remarkably small and helpless; in fact, more so than those of any other animal of equal proportions. Besides which, the full grown animals have very long hind-legs, and they progress by a series of extraordinary leaps. It would consequently be impossible for their helpless young ones to follow them: God has therefore given to female kangaroos and opossums curious pockets, formed out of their own skin, in which they place their little young ones, and bear them through their surprising leaps with the greatest ease and safety.