Hand drills were generally used in the early days of prospecting, and a sand pump drew out the sludge or borings for examination. This was superseded by the spring pole method, which in turn gave way to the rope method in use in the oil regions, the borings in each case being carefully preserved for inspection. The diamond drill is the one now in common use in the coal regions. Its cutting end is in the form of a circle set with black, amorphous diamonds. It cuts an annular groove in the rock as it descends, forming a core, which is withdrawn with the drill, and which may be examined in vertical section. The sludge is washed out by a stream of water which passes down through the centre of the drill rod, and is forced back to the surface between the rod and the face of the bore hole. The invention of this rotary cutting drill is due to Leschot of Geneva, and the method of flushing the hole to Flauvelle. After having obtained all possible information concerning his coal property, and, if he be wise, embodying it in the form of maps, the coal operator must decide where he shall make an opening for mining purposes, and what kind of an opening he shall make. The answers to these two questions are, to a certain extent, dependent on each other, as certain kinds of openings must be located at certain places. When coal was first gathered for experiment or observation, it was taken up loosely from the ground, where it had fallen or been broken down from the outcrop of some seam. As it came into demand for practical purposes, it was quarried from this outcrop backward and downward, as stones for building purposes are now quarried, the seam being uncovered as the work proceeded. This process was followed along the line of the outcrop, but excavations were not made to any considerable depth, owing to the great expense of uncovering the coal. The open quarry system of mining coal has been successfully practiced in America in but a few places. One of these was the great Summit Hill open mine, near Mauch Chunk, where the Lehigh coal was first discovered. Here, on a hill-top, was a horizontal coal bed, some sixty acres in extent, and varying in thickness from fifteen to fifty feet. Over this was a covering of rock, slate, and earth from three to fifteen feet in thickness. This bed was mined by simply removing the covering and taking the coal out as from a quarry. Other examples of this method are seen at Hollywood Colliery, and at Hazleton No. 6 Colliery, both near Hazleton, in Luzerne County. There are isolated instances of this method of stripping elsewhere in the anthracite regions, but as a rule the conditions are not favorable for it. Ordinarily there are four methods of making an entrance into a mine for the purpose of taking out coal. These are known as the drift, the tunnel, the slope, and the shaft.