Science Siftings

New Zealand Tablet, 21 May 1914, Page 49

Science Siftings

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When the Electric Lamp Burns Red. There is a certain similarity between the electric lamp and the old kerosene lamp. Both are everlasting barring accidents. But what most people forget, says Electricity, is that the filament of an electric lamp is .no more everlasting than the wick of the oil lamp. Both will burn out in time. Everybody who has used oil lamps knows and expects this. The difference between them and some users of electric lamps is that the latter fail to realise the fact. They expect the filament, or wick, to last as long as the glass globe in which it is enclosed. So when the lamp burns red and does not give its usually good light "they blame the electric light company for not furnishing 'good' current, whatever that may be. The fact is that when the lamp burns red and- dim the filament is about exhausted. Best then to replace it with a new one. It is consuming just as much current' as it did when its light was good, thus making a poor light as expensive as a good light. Every electric light company has a basis of exchange. What Becomes of All the Pins. What becomes of the millions of pins that arc used annually This question has puzzled for many years, but at last it seems to have been solved. Dr. Xavier, a Paris scientist, who has been experimenting on pins, hairpins, and needles by the simple method of watching a few of them closely from day to day, states that they practically disappear into thin air by changing into ferrous oxide, a brownish rust that soon blows away in dust. Dr. Xavier says that he found it took 154 days for an ordinary hat pin to rust and blow away, while a steel nib lasted a little less than fifteen months. A common pin vanished in eighteen months. A polished steel needle lasted the longest. It took two and a-half years for one to disappear. Eyes That Follow You. Have you ever wondered why the eyes in portraits painted in oils follow you? There is something uncanny about it. Years ago superstitious people were afraid to go into a picture gallery where portraits of ancestors were to be found. Now we know that the thing is simply an optical illusion. To produce such an effect the eyes of the person represented in the portrait must be looking directly to the 'front, and not towards one side. In such circumstances the pupil 4 of each eye is necessarily in the middle thereof, with as much ' white ' on one side as on the other. Obviously, this relation does not vary at all with the position assumed by the observer. The latter may stand far over on either side of the picture, and yet, from his point of view, there is as much ' white ' on one side of each eye as on the other, and the pupil still is in the middle. Such being the case, the painted image continues to look directly at him. In the palatial mansion of a well-known multi-millionaire there is a double staircase, the two flights joining at a landing above. On the wall is a huge painting of a flock of sheep coming downhill. The picture is a famous work of art, and cost many thousands of pounds, but the peculiarity about it that chiefly interests most people who see it is that, no matter which of the two flights (which are 50ft apart) one ascends, the sheep' seem to be running directly towards the observer. Here again the optical principle involved is exactly the same as that which makes the eyes in the portrait appear as if they followed you. '