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قراءة كتاب Asbestos, Its production and use With some account of the asbestos mines of Canada

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Asbestos, Its production and use
With some account of the asbestos mines of Canada

Asbestos, Its production and use With some account of the asbestos mines of Canada

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دار النشر: Project Gutenberg
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its value. It is used for a variety of ornamental purposes, for which, from its extreme natural beauty, it is peculiarly adapted. The grain is very fine and in its rough state the fibres are singularly distinct.

There is another very singular substance worth alluding to here, which is often put forward as a substitute for asbestos, and which is said by the manufacturers to be fireproof, frost-proof, vermin-proof, sound-proof, indestructible, and odourless. This is a good deal to say, but is in a great measure true. It is largely used in the United Slates, especially for insulating and other purposes of a like kind. I mean the artificially manufactured material called "Mineral or Slag Wool," which is made from the refuse of the furnaces at ironworks, by, it is said, passing jets of steam through molten slag. This material is manufactured on a somewhat extensive scale by the Western Mineral Wool Company, of Cleveland, Ohio. There is no doubt it is a very useful substance for many of the purposes for which it is recommended, but it can scarcely be expected to compete to any material extent with asbestos from its total want of elasticity and lubricity. Even the finest quality on being crushed between the fingers has a harsh, gritty, metallic feeling, very different from the silky, springy, and greasy feel of the natural fibre.

In connection with this manufactured article, a very curious natural production is called to mind, the origin of which is somewhat similar though brought about by natural causes. I refer to the product of the lava-beds of Hawaii, called by the natives "Pélé's hair." Miss C. F. Gordon Cumming, in her "Fire Fountains of Hawaii," speaks of this as "filaments of stringy brown lava, like spun glass, which lie scattered here and there, having been caught by the wind (when thrown up) in mid-air in a state of perfect fusion, forming fine lava drops, a rain of liquid rock, and so drawn out in silky threads like fine silky hair."

"In fact, this filmy, finely spun glass is known as Pélé's hair—Rauoho o Pélé. It is of a rich olive green or yellowish brown colour—a hint for æsthetic fashions—and is glossy, like the byssus of certain shells, but very brittle to handle. Sometimes when the great fire-fountains toss their spray so high that it flies above the level of the cliffs, the breeze catches it sportively and carries it far away over the island; and the birds line their nests with this silky volcanic hair. Sometimes you can collect handfuls clinging to the rocks to which it has drifted, generally with a pear-shaped drop attached to it." This, it is evident, would crumble and break off short in the fingers, and the mineral wool when handled has just the same gritty brittle feeling one can imagine Pélé's hair to have.

Returning to asbestos, however, its formation or actual origin is at present unknown. In its pure state it is as heavy as the rock in which it is found, so closely are its fine elastic crystalline fibres compressed together. These have a beautiful silky lustre, varying in colour from pure white to a dusky grey or green, sometimes of a yellowish green; the direction of the fibres being transverse to the walls of the vein. The essential point in which it differs from any other known mineral consists in its being at once fibrous and textile. Its quality is determined by the greater or less proportion of silicious or gritty matter with which its fibres are associated. When crushed out from the rock, these fibres, which vie in delicacy with the finest flax or the most beautiful silk, can be corded, spun, and woven into cloth in precisely the same way as any other textile fibre.

Of good quality it is only found in serpentine. One instance of its having been found in quartz is mentioned; but, even in that case we are told, when six feet of the superficial quartz rock had been blasted away, the inevitable serpentine was found cropping through.

According to Mr. Ells,[2] the serpentines in which it is found are intimately associated with masses of dioritic or doloritic rocks, of which rocks certain varieties, rich in olivine or some allied mineral, the serpentine is, in many cases, an alteration product. They are frequently associated with masses and dykes of whitish rocks, which are often composed entirely of quartz and felspar, but occasionally with a mixture of black mica, forming a granitoid rock. They occur generally not far from the axes of certain anticlinals which exist in the group of rocks called by Sir William Logan the "altered Quebec group."

For centuries asbestos was regarded merely as a mineral curiosity. Indeed, it is only within the last few years that it has developed into a valuable article of commerce, the first modern experiments in the use of it practically extending no farther back than 1850.

Its uses in the arts and manufactures are of a very important character, and now that it is clearly demonstrated that a fairly abundant supply can be obtained at a moderate cost, there seems no reasonable limit to be put to the demand, new uses for it being continually found. These will, of course, rapidly increase as its value becomes more clearly and widely known.

It is found in most parts of the world, but in only a few places of a sufficiently valuable kind or in quantities large enough to give it any commercial value. The main sources of supply at present are Canada and Italy.

A good deal has, at times, been found in Russia; and I remember an incident which occurred a few years ago at some extensive ironworks in that country, with which I was at the time connected, which amusingly illustrates how little was then known there of the nature and properties of the mineral. The iron ore, in the district referred to, is found in bunches or nodules, near the surface of the ground; and in order to get it, the peasants dig out pits about seven or eight feet in depth, and then burrow, rabbit-like, into the surrounding earth in all directions below. When all the ore is got out from one spot, they dig another pit further afield, and so they go on until the particular patch of ground they are working on is exhausted. On the occasion referred to, some of our men, in their burrowing, threw out a considerable quantity of asbestos. They had not the slightest idea what it was. In fact, they knew nothing at all about it, except that it was not what they were in search of; and, consequently, as it obstructed their work, they threw it all out in a heap near the piles of ore. Presently, one of the foremen or overlookers saw it, and wanted to know what all that rubbish had been put there for. "Here," said he, to some of the men, "just clear up all that mess at once, and fling it into the furnace, and get rid of it." And this was immediately done, with what result you may imagine.

Recently, however, it is said that enormous quantities of asbestos have been found in Russia, although I cannot learn that any use is made of it there at present. Its mercantile value must of course depend on its quality and distance from market. I have had a great number of specimens sent me, but they mostly turn out to be a coarse kind of so-called bastard asbestos, which would not pay for extracting. Now, however, we are told that from Orenburg to Ekaterinburg the country is thickly dotted with asbestos deposits, while near the Verkin Tagil ironworks there is a hill called Sholkovaya Gora, or Hill of Silk, which it is asserted is entirely composed of asbestos. The ore here is also said to be of the best white quality, well adapted for all the most important purposes to which asbestos is applied. I should much like to see a specimen of this; its

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