ASBESTOS. (FR., Asbeste ; GER., Asbest.)—Thia name, which is derived from the Greek word dA'sE0*TOS, incombustible, is given to aevera] varieties of amphibolie and augitio minerals. The commonest form occurs in massea of coarse, white, flexible, crystalline fibres, varying conaiderably in texture, and being sometimes so fine as to resemble silk, when it is termed "anzianthus." The fibres are found lying in parallel maases in extreme regularity, and may be easily separated one from another ; the individual fibres are flexible and elastic, of a white or greenish-white colour, and a fine silky lustre. Its chief peculiarity is that from which it derives its name, viz. almost complete incombustibility. A aingle fibre, exposed to a strong heat, fuses to a white enamel, but when woven together into a kind of coarse cloth it is capable of resisting the highest known temperatures ; it is also quite indestructible by acids.
Aabeatos has been known upwards of two thousand yeara. According to Pliny, it was used in his time for weaving ahrouds in which to wrap the bodiea of important personages before submitting them to the flames of the funeral pile ; or it was spun into cloths and napkins to be used at feasts or on state occasions. In those diatricts where it is found plentifully it has been used by the peasantry from time immemorial for making the wicks of lamps ; its power of capillary attraction renders it particularly applicable to this latter purpose. The art of weaving asbestos or amianthus into cloth seems to have consisted in interweaving fibres of flax with those of the mineral, and then subjecting the cloth to a atrong heat in a furnace. The flax was thereby consumed, and a fireproof cloth, com posed entirely of asbestos, obtained. The Chevalier Aldini, of Milan, has invented a much stronger cloth woven without the intermixture of any foreign substance ; the cloth is made loose in texture, and the fibres are prevented from breaking by the action of steam. The Chevalier has also contrived a fireproof dress, made of the same material, for the use of firemen. Some,yeare ago, the Societe d'Encouragement offered a prize for the improvement of asbestos cloth ; and the use of it was publicly shown in London in 1858.
The chief use of asbestos is for packing for steam pistons and pump-rods, stuffing-boxes and manhole plates, and to form a non-conducting covering for steam boilers and pipes : for all of these purposes it is specially adapted, owing to its power of resisting moisture, friction, high temperatures, and even flame itself. In Great Britain, the chief centre of the asbeatos manufacture is in Glasgow,
where experiments made with this substance have of late resulted in the production of many articles of utility, one of the most important of which is the covering for boilers and steam-pipes, mentioned above. This covering is applied like ordinary cement or plaster, and is easily manipulated.. A single layer, 1 in, in thickness, is amply aufficient. Its own adhesive properties render the assistance of other cementiog material auperfluous. The cylioders of some steamers have been covered with this material with complete success. The price of this covering is the same as that of the ordinary kinds. An asbestos jointing in the form of a paste or cement, is also manufactured at Glasgow. On account of its impervious resistance to acids, oils, high-pressure steam, hot water and sugar liquors, this substance claims to be far more durable than those applications which have been formerly restricted to white and red lead or indiarubber. A mill-board jointing made of asbestos is also becoming an article of considerable importance as an economiser of labour in machine shops; it can be effectively and reliably used on a rougher face than any other ; and thus the tedious and lengthy processes of " getting up " or " facing" are obviated.
In America, where asbestos is becoming an article of extensive manufacture, it is employed in preparing a kind of lining, or sheathing paper, for ceilings, walls, and floors. These papers are made in rolls of any length or thickness, and can be printed with any pattern ; not only do they render the building safer in case of fire, but they also have the desirable effect of keeping it cooler in summer and warmer in winter. Audesley, who owned considerable deposits of asbesb?s near Baltimore, introduced asbestos paper into the States with much success. Owing to the friability of paper made from asbestos, it can only be applied to coarse purposes, although it is not impossible that its peculiar property of resisting heat might be of use under some circumstances. In 15a3, a patent was taken out for the preparation and use of asbestos for this purpose. The pulp was mixed with alum, and an indestructible paper produced ; this paper burns with a flame, leaving a white residue, which retains the shape of the paper if carefully handled. Any writing in common ink is perceptible even after the organic substance of the paper is consumed.