Rock Boring; Rock Drilling Explosives and Blasting Coal-Cutting Machinery Timbering Timber Trees Trackwork

This historic book may have numerous typos and missing text. Purchasers can download a free scanned copy of the original book (without typos) from the publisher. Not indexed. Not illustrated. 1907 Excerpt: ...and blasting in coal will be found in Drifts, Slopes, and Shafts, and Methods of Working. COAL-CUTTING MACHINERY GENERAL PRINCIPLES OF MACHINE COAL CUTTING INTRODUCTION 1. Cutting the Coal.--The most expensive and difficult operation in the production of coal is, in general, the process of loosening it from its solid state. This is accomplished in three ways: (1) By blasting it from the solid, as is done in most of the mines in the anthracite regions and in many bituminous mines. (2) By undercutting and blasting or wedging down, or letting the weight of the roof break the coal; this method is used in many bituminous mines worked on the room-and-pillar system, and in all longwall workings. (3) By shearing the coal, either in the center or on one rib, and blasting. In some mines, the coal is both undercut and sheared, either on account of a frail roof or to produce a larger proportion of lump coal; for when the coal is both undercut and sheared, it can be brought down with a very light charge of powder. 2. The many machines that have been constructed to undercut and shear coal are now so perfected to meet the various requirements found in the different fields that an increasing number of mines each year is being equipped with coal-cutting machines. The use of these machines enables the operator to increase his output with a given amount of labor and reduce the cost of production, and permits the operation of a mine with a smaller number of skilled miners. CefyrizkUd by International Textbook Company. Entered at Stationers' Hall. London Results obtained in machine mining have generally been satisfactory wherever the machines have been installed with prudence; that is to say, wherever the proper type of machine has been carefully considered and good judgment us...