Collection: Directories and Documents

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Title: A Descriptive Treatise on Mining Machinery, Tools, and Other Appliances Used in Mining - Volume 1 (1877) Collection Type: Directories and Documents Author: George G. Andre Published: 1877 # of Pages: 311 Download PDF: User Login Required Download OCR Text: User Login Required

Date Scanned: 2025-05-04 16:56:34 OCR Software Version #: tesseract 4.1.1 Item Sourced From: PDF First Created: 2025-05-05 01:05:02 Last Updated: 2025-05-05 05:59:57

Digital Copy Held At: Searls Historical Library Location: 161 Nevada City Hwy, Nevada City, CA 95959

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8 MINING MACHINERY. similar to that used for boring in wood. The bottom is partially closed by the lips, which are turned down to a greater angle than in the case of wood augers. The clay auger is made of greater lengths than the chisel bits, but it terminates upward in the same form. Usually it is half cylindrical, as in the figure; but sometimes it is made wholly cylindrical, with the exception of a length of about 6 inches at the bottom, where it is left open to allow of the admission of the material which is being bored through. When used in clay, this tool, on being raised to surface, carries the “ core” with it. For clearing the bore-hole of the debris of the rock chipped off by the cutting tool, an instrument called a “sludger,” Fig. 19, is used. This instrument is so called, because it removes the debris in the form of sludge or mud. It consists of a wrought-iron cylinder, a little less in diameter than the cutting tools, the lower extremity of which is furnished internally with a ball-valve. This valve is of metal, and its weight is proportioned to the degree of fluidity of the matters to be extracted. It is made to rest upon a conical seating formed by an annular piece riveted to the cylinder. The sludger is worked by jerking it up and down in the bore-hole on the end of a rope. During the descent of the tool, the valve is raised by the water in the hole, and as it sinks by its own weight into the debris, the latter passes above the valve. During the ascent of the sludger, the material which has entered acts, with the water, to close the valve. By this means, the escape of the sludge is prevented, though a large portion of the water passes out through the accidental interstices caused by small pieces of stone upon the valve seating. The action of the sludger is very effective, as much as a cubic yard of sludge being sometimes removed at one time by a large tool. When the operation of “pumping” the sludger has been continued sufficiently long to clear the hole, it is raised and its contents removed by turning it upside down. This instrument will be found illustrated again among the American tools, where it is described as the “ Sand-pump.” The materials brought up by the sludger show the nature of the stratum that is being passed through. But as these materials are in a divided state, being reduced to small fragments by the action of the chisel, they indicate but little of the physical condition of the rock-bed, and nothing whatever of its dip. Moreover, their indications concerning the nature of the bed are hardly trustworthy, inasmuch as particles of the higher beds are continually falling from the sides of the bore-hole. As it is highly desirable that full information on all points should be obtained when boring in search of minerals, and especially on the dip of the beds, their physical character, and their geographical age as evinced by contained fossils, it becomes necessary to have recourse to special tools for that purpose. The use of such tools is to bring up asolid core of the rock, and to bring it up in such a condition that the lines of stratification will show the dip of the bed. To obtain this result, the core must be marked relatively to the north point before it is broken from the rock. This is effected by means of a chisel with an eccentric cutting edge. Having previously cleared out the hole, this chisel is lowered, care being taken, by suitable marks on the rods and a fixed plumb-line, that it be not turned in the least degree during the operation. When it has reached the bottom of the hole, two or three light blows are struck without turning the rods, and it is again raised. A special tool, Fig. 17, composed of a number of chisels set in a ring, is then lowered, and worked with light blows in the same manner as the common chisel. By this means an annular space is cut round the marked core. When this space has been cut nearly to the depth of the chisel, the tool is raised, and another special extracting instrument, Fig. 18, let down. This instrument drops over the core, and by means of a wedge thrust in by the weight of the rods, exerts