SCIENCE NOTES & NEWS.

Waipa Post, Volume VII, Issue 331, 17 July 1914, Page 7

SCIENCE NOTES & NEWS.

PREPARING A CRACKED WALL FOR PAINTING OR PAPERING.

When a plaster wall or ceiling is so badly cracked that it will not do to paint or oven paper the surface, cover it with a strong muslin or light canvas. Use a strong paste made of flour in the ordinary way with a little glue 'added to give it stronger holding qualities. Press out any air bubbles that may occur and make tho surface quite smooth. Either water or oil colors, as well as paper, may be applied to this surface, and it will make a very smooth and sure job.

THE VALUE OF SAWDUST.

Sawdust is being put to an increasing number of useful 1 purposes. Used as an absorbent for nitro-glycefine, it produces dynamite. Used with clay and burned, it produces a terra-cotta brick full of small cavities that, owing to its lightness and its properties as a non-conductor, makes excellent fireproof material for walls or floors. Treating it with fused caustic alktili produces oxalic acid. Treating it with sulphuric acid and fermenting the sugar so formed produces alcohol. Mixed with a suitable binder and compressed, it can be used for making mouldings and imitation carvings. If mixed with Portland cement it produces a flooring material.

WIRELESS NIGHT MIRROR TO MAKE THE SEAS SAFE.

A remarkable invention pregnant with useful possibilities is the wireless long-distance mirror. Its purpose, in brief, is to convey an imago in the same manner that sounds are now communicated.

It is a radical improvement of the old-time camera obscura, a structure in which the real image of an object is projected upon a white table or other plane surface. Not only doesJ.be new apparatus reflect on a mirror all objects located and all happenings occurring within a much greater area than the camera obscura, but it operates at night. Just how the machine works has not yet been revealed, but the machine is known to consist of a web of wires attached to a tall mast, and it is this web of wires which receives the impressions and projects them on to the mirror located at the base of tho mast.

The principal value of the now apparatus will be in its application to ships. It is expected to prevent collisions with other ships, icebergs, or derelicts by disclosing the whereabouts of such dangers to the look-out long before the vessel comes within striking distance. Tlie image of every object within a radius of two or three miles is thrown on to the mirror, and at night or in fog tlie value of such an apparatus to the mariner could piardly be over-estimated. It is claimed, too,, that the longdistance mirror would prove a valuable aid to armies in time of war, revealing the whereabouts and movements of iho enemy in a manner which would make all other forms of reconnoitring seem entirely inadequate. A test was recently mode at Vallejo, California, and the, instrument was said to accomplish all that had been claimed for it. The night was dark, but a perfect picture of the district within a radius of two miles was clearly shown on the mirror. All the activities of tlie Mare Island Navy Yard, railway trains passing up and down the valley, and pedestrians in the city streets wore clearly shown.

CHANGING THE COMPOSITION OF IRON.

Castings and forgings of soft iron can be quickly transformed into hard steel by a‘ newly patented, electrical process for changing' the composition of iron or steel. By the use of an electrical furnace the entire mass of metal or any depth of surface can be hard-, ened and tempered in a few minutes. The old process of changing the composition of iron or steel by cementation is extremely slow; and the more rapid process of caschnrdcning with potassium cyanide, or some other tempering substance, produces only a thin superficial skin of harder metal: Both arc faulty because of the difficulty of applying the carbonizing substance while the iron is heated near the melting point. In the new process, the iron 6r steel is completely inclosed in a hardening mixture in a small furnace and an electrical current passing through it heats it above the welding point so that the change in composition takes place in a few minutes.