SCIENCE SIFTINGS

New Zealand Tablet, 11 August 1921, Page 46

SCIENCE SIFTINGS

(By '‘Volt.’’)

Damming Water with Water.

* Experiments by Norwegian engineers have shown the possibility (says a writer in the Engineering News-Record, New York) of successfully damming shallow streams by means of a large canvas hose filled with water. The dam was constructed October 26, 1920, across the Skjaersjo River, Maridalen, Christiania. We read; —“Where the dam was located the stream is shallow afid has a rock bottom. The hose used was of cotton canvas and was lIS feet long and 6.56 feet in diameter. It was laid across the river enclosed in a rope net anchored by cables to bolts set in the rock bottom about 65 feet up and down stream from the hose. Both ends were also anchored to the shores. One end of the hose was temporarily closed by a plank clamp and the other end was left open and was slightly elevated for filling. The hose was filled with water run into the open end by a small hose laid far enough up-stream to get a filling head of water. It required about twenty minutes, with a 7.8-inch filling hose, to fill the large hose to the condition suitable to the nature of the dam, about 6 feet high, which was formed. For more permanent structures it is contemplated that the hose will be filled with liquid mortar. The method, which is patented, has been planned for various other uses in engineering construction. Johan Store, civil engineer, Christiania, Norway, is the inventor.”

Wonderful Timekeepers.

As far back as 300 B.C. the Egyptians used a clock which was worked by water. The passing of water through various pipes moved a cog-wheel with a hand attached, and this hand indicated the different hours of the day while the wheel performed its revolutions.

Hour glasses, or sand glasses, were invented about 330 A.D. They were made of two bulbs of glass with an intervening neck. Dry sand placed in the upper bulb ran through the. neck into the lower bulb in exactly one hour. Clocks worked by weight were in use in 1125, but watches were not invented until 1500.

Typewriters,,for the Blind.

An ingenious typewriter for the use of the blind has been invented by Natale Rovedo a young Milanese artisan.

Its method is modelled on the ordinary but obsolete German portable printer Mignon, only a zinc plate is introduced containing forty-two spaces, within each of which is set in relief one of the characters of the Braille alphabet. , *.

The operator places the index finger of the left band in the finger guide, which moves over this zinc plate, and, having found the required sign, strikes the stamping lever with his right hand. The chief merits claimed for the machine are its Economy and ease. After two days practice the inventor s sightless comrades learned to write sixtyfive letters a minute. '

Where Hail-Storms Start.

The starting point of a hail-storm is a layer of air laden with water-vapor.

This passes rapidly through varying degrees of temperature, which first freeze the particles of water and then melt them and re-ireeze them, adding other particles as the journey continues." *

Hail-stones, in falling, are sometimes carried below the central part of the storm which gave birth to them, through successive layers of rain or snow, which accounts for the fact that the resultant stone is formed of a number of distinct coatings, like the skins of an onion.

It frequently happens that a considerable quantity of this frozen vapor is whirled by the action of the storm into the centre of the tornado. Then, when the force ceases abruptly or the particles become too heavy to be supported by the wind, they fall to the earth in an almost solid mass. The connection- between hail-storms and thunder-storms is because of the rapidly shifting degrees of temperature which accompany the latter—a fact which explains also why hail-storms occur usually in the spring or summer, when the majority of thunder-storms take place. '