Science Sittings

New Zealand Tablet, Volume XXXVI, Issue 17, 30 April 1908, Page 35

Science Sittings

* . Thermometer and Wind. Many persons, if asked about it, would say "that the thermometer is affected by the wind, but it is not. If you stand out where the wind can blow freely over you, you feel the cold much more than you do when sheltered— say, by the corner of a building— but it is different with a thermometer. Try it by hanging up t(wo thermometers, one in the wind and the. other in a sheltered place wear by, and you will find that they mark' the same temperature, everything else being eqjual.Wind is merely air in motion, and the motion does not make it colder. You feel the cold more sensibly when exposed to it because the current of air 'takes heat away from your body. Caterpillars. The caterpillar spends his time trying to keep out of everybody's way. Some species hide on. the under surface of leaves, others on , the steir® or blades of grass, which serve them as food ; others again build little nests for concealment or else they lie snugly hidden between the curled edges of leaves, which they •draw close together until the opposite edges meet. The caterpillar 'is a sociable creature in his own family. He knows that there is safety in numbers, and you will find whole companies feeding side by, side while keeping a sharp look-out for their bird enemies, but when a caterpillar is by himself he scarcely dares to move for fear of attracting attention. Even when he is obliged to change his skin he doesn't venture to leave his old coat lying around. The moment that he takes it off he eats it. The caterpillars that live in companies shed their skins boldly. Only the poor solitary fellows feel forced to. swallow their old clothes. Why the Sky Looks Blue. It is the atmosphere that makes the sky ' look blue and the moon yellow. If we could ascend to an elevation of fifty miles above the earth's surface, we should see that the moon is a brilliant white, while the sky would be black, with the stars shining as "brightly in the daytime as at night. Furthermore, as a most picturesque feature of the spectacle, we should notice that some of the stars are red, otihers blue, yet others violet, and still others green *in color. Of course, all of the stars (if we bar the planets of our own systero) are burning suns, and the hues they wear depend upon their temperature. The hottest stars are blue. Thus Vega, in the constellation Lyra, is a blue sun hundreds of times as large as our solar orb. We are journeying in its direction at the rate of millions of miles a day, and at some future time it may gobble us all up. For, after all, humiliating . though the confession be, our sun (says ' The Reader ') is only a very small star— of the sixth magnitude or thereabouts — and of an importance Sn the universe so slight as to be scaroely within the pale of respectability.

The Duck-billed Platypus. The remarkable animal known as the duck-billed platypus (says the ' Weekly Telegraph ') is found, in Tasmania and in the south and east of Australia. When specimens were first introduced into England it was fully believed that they were manufactured by some impostor, who., with much ingenuity, had fixed the beak of a duck into the head of some unknown aawanal. Besides this peculiarity of the duck-like beak, the platypus is- also remarkable as being one of the few mammals which brings its young into the world in tne shape of eggs. Its feet are webbed, aiwl its spends- a great part of its life in the water, extracting worms, insects, etc., from the banks and beds of the rivers that it frequents. It lives in burrows made in. the river bank, one entrance being under water whilst the other is some distance inland, among grass or rough brushwood. The burrows are of great length, some measuring fifty feet in length. At the end of the burrow it places 'its nest, composed of weeds, grass, and root fibres'. Here it lays 'its eggs, genertfly two hi number, and rears 'its young.