Page:Popular Science Monthly Volume 91.djvu/784

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��Popular Science Monthly

��when it is to be used in sanding machines, there is an additional backing of cloth. Garnet-paper is not so sharp as sandpaper, but it has the advantage that the edges and corners of the particles do not wear smooth, but break off at sharp angles. Hence it cuts satisfactorily just so long as it adheres to the paper.

��Emery

Emery is a variety of corundum, and is sec- ond only to the dia- mond in hardness. When used for the abrasion of metals, it may be spread on the surface of paper, cloth, or wood. In this shape it is used mostly for smoothing and polish- ing metal. Emery may also be mixed with a kind of earthenware, and then baked, to make "emery stone." Emery wheels are thus made, and they are so hard and strong that they can be revolved at a high velocity, to cut very effectively. Emery in its powdered form is used to grind valves to their seats and to make them airtight.

Whetstones are quarried and cut from natural rocks, found mostly in Arkansas. The best ones are found near Hot Springs, Ark. The coarser ones, such as are used for whetting scythes, etc., are called Washita stones, while the fine white ones are called Arkansas stones.

Other natural abra- sives used in the arts are tripoli, made from a sili- cious sandstone, and used for polishing horn, shell and metal; rotten stone, an infusorial earth, used in rubbing down varnish ; pumice, made from a volcanic ash, also used in rubbing down varnish

�� ��Whetstones are quarried and cut from natural rocks found mostly in Arkansas

��Emery is second only to the diamond in hardness. It is the strongest abrasive

��and rouge, made from sulphate of iron, and used for polishing glass. It will be observed that all of the abrasives mentioned are mineral products except the steel wool.

��Half-Soling Rubber Overshoes to Give Longer Wear

AS rubber overshoes are still in high favor l as a necessary evil for keeping the feet dry in muddy or wet weather, any idea that promises to make the rubber give longer

service should appeal to

economical people.

A friend of the writer gets more than double wear out of his rubber overshoes by half-soling them with rubber. He owns an automobile, and when the soles of his overshoes become thin, but are still watertight, he takes a torn and other- wise useless inner tube and cuts a half-sole from it. This half-sole is then cemented to the rubber shoe — after both sole and shoe have been cleaned thoroughly and roughened with sandpaper — u sing ordinary rubber cement and clamping or holding both tightly together so that a secure union is obtained. The same kind of cement is used as for repairing bicycle tires, and if used according to the directions that accompany it, a satisfactory job will result. An attached sole of this kind will^often give longer wear than the original. If the heels also are worn, they can be repaired in the same manner. If you can- not procure an old rubber inner tube, most any kind of pli- able sheet rubber will do, providing it is of the proper thickness. Halfsoles for arctics have been made from a piece of large-size rubber hose, split and straightened, and have given excellent service. The rubber used for this purpose must not be hardened from age.

If it is not possible to procure an old piece of rubber, an extra half-sole or heel can be purchased from a rubber dealer. These come in different sizes and shapes.

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