Science Siftings

New Zealand Tablet, 18 January 1912, Page 41

Science Siftings

By Volt.*

The Hourglass,

Instead of being obsolete and simply an interesting relie, the hourglass in various forms is a twentieth century necessity. For such purposes as timing, hardening and tempering heats in twist drill manufacture, where seconds or minutes must be gauged accurately, nothing serves like the hourglass with the right amount of sand. Accuracy to fractions of a second can be obtained much more easily by an hourglass than by watching the hands of a watch.

The Screw.

: The invention of the . screw is generally attributed to the old Greek Archimedes, from all accounts one of the greatest scientific thinkers and mechanicians the ancient world ever , knew. The screw, is one of the greatest things in mechanics, simple as it is, and aids immensely to the unaided human power. It is claimed that one man, with the help of the screw, can press down or raise up as much as 200 men can without it. In addition to the invention of the screw, Archimedes invented the sunglass, various devices for battering down walls, and some half-dozen other valuable ways and means of providing power.

To Telephone with Light Rays.

Inventors have been busy for .some years trying to make a practicable system of wireless telephony in which the medium of communication is a beam of light. The most recent device in this line is the invention of a Frenchman named Ancel, and is an improvement on

an : earlier form devised by. Ruehmer.. It is seemingly perfect in operation, but not likely to be used practi-; cally, 5 because / anything; that vents off ’ the' light between the transmitting and the receiving station also puts a stop to communication. / ■ The Pressure of Water. . ■ A bottle partly filled with fresh water, and tightly corked ‘ can be lowered into ocean depths,/and on being raised to the surface ‘it will ; be discovered on opening it that the fresh water has been replaced by salt. This really extraordinary phenomenon is explained by the New York Tribune in the following way.: —-The pressure of water increases as the distance from the surface down? ward. Thus at the; distance of a foot beneath the surface the * pressure of ; the water a square r inchwill be about half, a pound; at a distance of, say, 200. feet, it will be 1251 bto the square inch. At ocean level -the pressure of the atmosphere is. a little over 141 b. Thus if a bottle containing air were lowered some 30 feet beneath the surface the pressure of water would more than counterbalance the pressure of the , air. Ordinarily at this depth, therefore, the pressure of water should be sufficient to drive the cork within the bottle; but the cork is tightly wedged in position. To squeeze it within the bottle it, too, must first be compressed, and also there is friction to be overcome. ' The distance varying, then, according to■> these conditions, at some•; point beneath the surface the weight of water will force the cork into the bottle, compressing the air before it. The salt water of the ocean mingles with the fresh water within the bottle. As the bottle again approaches the surface, the air that remains within is subjected to less and less pressure till finally, ! now having- given itself a , pressure greater than that, of water, it drives the cork back into position. - * ’ *