Science Siftings

New Zealand Tablet, Volume XXXVI, Issue 25, 25 June 1908, Page 35

Science Siftings

By VOLT

Phoning Through the Earth. The most interesting experiments in telephoning without wires are those of the French scientist Ducretet. He places an ordinary telephone transmitter in direct communication with the ground, and at a considerable distance away, on the other side of some buildings with thick walls and cellars, he has a receiver, connected by one wire to the earth, and by another wire to a small metallic sphere let down through an opening to the lioor of the catacombs beneath Pans. When words are spoken in the transmitter they are heard in the receiver with much greater clearness than in an (ordinary telephone. Monsieur Ducretet is continuing his experiments at increasing distances. When to Wind a Watch. At a recent meeting ol the British Watch and Clock Mabers' Guild the question whether it is better to wind a watch at night or in the morning was discussed. Some members were of the opinion that it was better to wind it at night, as in the morning the mainspring would be colder than it would be after being carried about in the pocket all day, and steel is more brittle when cold than when it is warm. Mr. Wright, the vice-president, said that, during the day the watch was carried about and subjected to all kinds of irregular conditions, and when it was fully wound it was able to withstand these abnormal conditions better than when it required winding. He thought it was a decided advantage to wind it up in the morning. This view of the case was agreed to by the majority of the members of the trade who were present. Curious Deceptions. Our senses deceive us curiously at times. A flash of lightning lights up the ground for only one-mil-lionth of a second, yet it seems to us to last ever so much longer. What happens is that the impression remains in the eye or the retina for about one-eighth of a second, or 121,000 times as long as the Hash lasts. If on a dark night, a train speeding along at sixty miles an hour is lit up by a lightning Hash it appears stationary, yet in the eighth of a second during which we seem to see it the train travels eleven , feet. But we really only see it during one-millionth of a second, and in that time it travels only one-hundredth of an inch. When a man's leg is cut off, if the stump be irritated he feels the pain in his toes. This curious deception is the same as any one can practise on himself 'by striking his elbow "on the table, when he feels the pain in his fingers. Of course, in both cases the pain is felt in the brain. We do not actually perceive different distances with the eye, but judge them from various indications. When our judgment is at fault we are deceived. If you see a person in a fog, for instance, he seems to be much bigger than usual. The same thing happens when you see men or cattle on the top of a hill against the horizon in twilight. In both cases you judge them to be farther away than they really are, and consequently they appear uncommonly lange. The First Gas. Soon after Argand invented his lamp, William Murdock, a Scottish inventor, showed the world a new way of lighting a house. It had long /been known that fat or coal, when heated, gives off a vapor or gas which burns with a bright light. Indeed, it is always a gas that burns, and not a hard substance. In the candle or in the lamp the flame heats the oil which comes up to it through the wick and thus causes the 1 oil to give off a gas. It is this gas that burns and gives the light. Now Murdock, in 1797, put this principle to a good use. He heated coal in a large vessel, and allowed the gas which was driven off to pass through mains and tubes to different parts of his house. Whenever he wanted a light he let the gas escape at the end of the tube in a small jet and lighted it. Here was a lamp without a -wick. Murdock soon extended his gas pipes to his factories, and lighted them with gas. As soon as it was learned how to make gas cheaply, and conduct it safely from house to house, whole cities were rescued from darkness by the new illuminant.