Science Siftings

New Zealand Tablet, 22 June 1911, Page 1171

Science Siftings

BY ‘VOLT’

A Bomb Cannon.

Krupp’s latest engine of war is designated as a ‘bomb cannon.’ Its function is to hurl a blast of stifling smoke and fire, eliminating every possibility of life within its immediate vicinity at the instant of explosion. The bomb itself is quite large and is fitted with a metal cover just stout enough to hold the charge. The action of the fragments are of little consideration when compared with the effect of the smoke, fire, and pressure of concussion.

A Rust-proof Steel.

An English firm has succeeded in manufacturing a steel proof against the corroding influence of smokeless power and rust. During trial 5000 cartridges containing 43.21 grains, Troy, were discharged through a rifle barrel made of this product without a trace of any deleterious action on the metal. The intervals between the firing covered a period of some fifty days, during which time the gun was purposely kept uncleaned and in a damp locality.

How a Priest Invented the Deaf and Dumb Alphabet.

A French priest, the Abbe de I’Epee, once saw two sisters whose eyes looked up into his very intelligently, but whose tongues could not speak, nor could their ears hear. They were deaf-mutes. lie wondered if it were possible to help them. If, later on, we could have peeped into the rooms of this good priest, we might have seen him twisting his fingers about. We might have noticed that the gestures made by his fingers were in the form of letters —something like letters. We could easily tell OorTor V. He was inventing the deaf-and-dumb alphabet. The next thing was to teach it. Ah, what a labor it was to teach the deaf! But the kind priest was very anxious to help the poor childrenthe two sisters were his first pupils—and so it was what we call a ‘labor of love’; and of course the Abbe succeeded in it. Before he died in 1789, at the age of 77. very many young people had learned the alphabet ‘ finger talk ’ — his classes. Of course, as you may know, this finger language is not so much used now, because the deaf-mutes are taught to speak with their lips; but for a long time the only way they could speak was by means of the Abbe’s alphabet.

Comets not Self-luminous.

After a careful study of the observations made on Halley’s comet by the various observatories of the world, Dr. Eginitis, of the observatory of Athens, draws the interesting conclusion that comets are not self-luminous bodies, but rather shine by reflecting the sun’s rays. During its last visit it was observed that as _it approached the earth the tail became more dim, and just before its conjunction on May 18, it grew even dull, as if composed of smoke, which disappeared at the first light of dawn. However, after its passage to the other side of the earth, on the 19th, the portions seen in the west suddenly took on an intense brightness, which made them easily visible to the naked eye. even at twilight. This was not a difference due to the varying angle at which the tail was observed, but was a sudden transition through five magnitudes. , After May 21 the tail, according to the usual law, grew dim, as is always the case with a reflector receding from the sun and from the eye. A similar phenomenon, though not so marked, was observed with regard to the head. It grew bright as it approached the sun until April 1, remained invariable for about a month before inferior conjunction, increased to first magnitude by May 21. then grew dim. Theoretically, its brightness should have been fifteen times as great as actually observed, and the same is true of the nucleus.

To Make Cement Waterproof.

Concrete and cement mortar are being used more and more as construction materials on the farm. _ Whatever simple devices are brought forward for increasing waterproof qualities of these materials are welcomed. In order to make concrete and mortar more impervious to water it is customary to add some foreign material, as, for instance, clay. The clay must be —that is, not intermingled with vegetable matter. Besides being pure, it must be finely “powdered. Of course, it is difficult, well-nigh impossible, in fact, to lay down a set rule, for amounts added vary with the mixture. But add from 3to 4 per cent, of the"weight of the sand used in the mixture you are dealing with. Mix the clay dry with the cement. In the case of cement mortar, an addition of soap and alum gives good results along this line of water tightness. Suppose the mixture is one part of cement to two and a half of sand. Then add three-quarters of a pound of powdered alum for every cubic foot of sand. Mix them dry and add to this mixture water in which soap has been —laundry soap may be three-quarters of a pound to a gallon of water. The resulting mortar, while having gained in water tightness, has lost something in strength. Walls which extend below the ground level are often damp. To prevent moisture passing through, apply two coats of good tar. The coating should extend above the ground surface. This is a simple and effective device.