An air compressor reversed in direction is an air exhauster, such as we find carrying money in department stores. The powerful in-draft of this apparatus, often drawing large pieces of paper or card into the pipes, has led to the invention of a means of removing dust and dirt, admirable in thoroughness. A receiver, shaped to suit its special task, is passed over pictures and their frames, upholstery, carpets or bare floors, and through the flexible pipe attached to its handle, dust and dirt are borne into a reservoir where they are caught by water for due removal. Ordinary sweeping with a broom, the usual wielding of a feather duster, or a blast of compressed air, but stir up dust and dirt for harmful redistribution. This “vacuum” cleaning method takes dust and dirt wholly away, and with wonderful celerity. See [picture] opposite page 164. It is astonishing to see a pound of fine flour removed from a thick carpet in twelve seconds, leaving behind not one visible particle. This plan cleanses carpets without their being lifted from floors, or a billiard cloth just as it stands on a table. This service greatly promotes health; the further the physician goes with his microscope the more convinced is he that dust is one of the chief carriers of disease.
Hardie nozzle for painting by compressed air.
Not only dust but sand may be borne when a breeze rises to a gale.
Sand-blast.
In Lyell’s Bay, near Wellington, New Zealand, and in many other places throughout the world, flints have been found so beautifully and symmetrically polished that they were at first believed to be products of art, yet nothing but wind-blown sand had given them form. Fifty years ago globes for gas jets were frosted by a handful of sand quickly thrown from side to side for a few minutes. Strange to say, gunnery was to supply the link to carry sand to labors of much greater moment.
Vacuum renovators for carpets and upholstery.
General B. C. Tilghman, of Philadelphia, one day noticed the much worn touch-hole of an old bronze cannon. He felt sure that the wear had been due not so much to outflowing gases as to bits of unburnt powder driven out at each discharge, identifying this abrasion with the roughening of glass in windows facing sandy shores of the sea. In 1870 he began experiments by blowing sand jets with a fan, soon discovering that he had hit upon a cheap and easy means of frosting glass, carving stone, and scouring castings. He was astonished to find that sand readily pierced materials harder than itself, as corundum and toughened steel. To-day the sand-blast executes many new tasks: it resurfaces stone buildings which have become discolored and grimy; it cleanses metallic surfaces for the welder, the electroplater, the enameler; it renews files and rasps; it removes scale from boilers, paint and rust from steel bridges and other structures. The apparatus manufactured by Mr. C. Drucklieb, of New York, designed much in the form of a steam injector, employs air at a pressure of about twenty pounds to the square inch.