the conveyance of mineral and material underground and on the surface, for rock drilling, and stamping, a severe system of finance adhered to, and, as a result, the British coppermines found capable of holding their own in competition with the world. 31 CHAPTER II. EXPLORATION. It THE mining engineer may find himself in a country to which he is a stranger, his duty being to ascertain what valuable minerals, if any, exist in the locality, and their mode of occurrence. would greatly facilitate his inquiries and enhance the value of his discoveries if he had been a diligent student of geological science; and the following pages are intended, not as any substitute for such study, but partly to point out how such study would be useful, as well as the methods he would pursue if his previous study had fitted him for the work he has undertaken. It may FIG. 39.--Showing plan of estate and vicinity. Bore-holes and trial holes shown O. simplify our treatment of this subject if we consider, in turn, some of the numerous problems that present themselves in practice. Case I. The particular bit of country he has to explore is in a coal-field. It is indicated in Figs. 39 and 40. The plan and section show the result of the exploration. Two collieries are discovered on the west and east: that to the west being on the "rise" side of the estate, or the side on which the strata crop out; that to the east being on the "dip" side of the estate, or the side on which the strata dip under other and superincumbent strata. The depths of the shafts are respectively 120 yards and 360 yards from the surface to the lowest seam of coal, which is 4 feet thick. The west colliery is 20 yards above sea-level, and the east colliery 60 yards above sea-level; thus the respective depths below sea-level are 100 yards and 300 yards, as shown in the section figure. Each colliery is working a similar coal, apparently the same seam, dipping in the same direction at the same rate. A thin seam of coal, 2 feet thick (No. I on the section), is found cropping out on the hillside, at a height of 45 yards above sea-level, dipping east at an angle of about 3°; a similar and apparently DIP ABOUT 3° FIG. 40. Showing section from west to east across the estate. The sketch is identical seam is found in the east colliery shaft, 125 yards below sea-level, and at a distance of about 3400 yards from the outcrop. It is then noted that a dip of about 3° is approximately equal to a dip of 1 in 20, or 5 per cent.; that is, a dip 1 yard vertical in a distance of 20 yards horizontal. This dip, continued for a distance of 3400 yards horizontal, would give a vertical fall of 170 yards, and that is precisely the fall that is found-45 yards, above sea-level added to 125 yards below. There are also three sandstone quarries in two distinct beds, where freestone is got. The dip of the strata is here ascertained to be about 3° east, and at a corresponding depth the same two beds of rock are found in the east colliery shaft. On the top of the hill some trial holes are dug 6 or 7 feet deep into the beds of shale, and here the dip is also found to be regular at 3°. The outcrop of coal No. 1 is traced along the hillside across the estate from north to south, either by digging with a pick and shovel, or by boring holes, say 5 yards deep, with boring-rods. The eastern outcrop of the upper bed of rock is also traced across the estate from north to south. The exploration of the estate is now complete. The uniformity of the dip from west to east, as proved by the pits, outcrops, quarries, and intermediate trial-holes, shows that there is no fault or break in the strata between the two collieries. The regularity with which the outcrops of coal and rock follow ·-600 YDS- FIG. 41.-Plan showing "wash-out." the contour of the hill show that there is no fault from north to south. It is, therefore, reasonable to believe that the coal and other strata found in the east colliery continue regularly under the estate, as shown on the section. It is possible that in the distance between the east and west collieries some beds of coal, fire-clay, ironstone, shale, and rock may vary in thickness and quality, or may be in places entirely wanting. It would be very remarkable, indeed, if a coal-seam 4 feet thick were to be entirely wanting in such a situation. But it is a contingency to be guarded against. There are "wash-outs," sometimes called "dumb-faults." These are places from which the coal has been washed away as if by some river, and the river-bed afterwards filled up with sand. These wash-outs are sometimes 600 yards in width and 7 or 8 miles in length. Figs. 41 and 42 show a plan and section of a wash-out. Referring to the plan (Fig. 39), it is possible that such a washout may traverse the estate from north to south. If there are D no collieries north and south by which the coal is proved, there is no means of ascertaining that such a wash-out" does or does not exist except by a number of costly borings. Wash-outs are very rare, and, if the estate was in other respects satisfactory, FIG. 43.-Plan of estate, showing outcrops thus; pits, O; bore-holes, O. most mining engineers would consider that the coal was sufficiently proved. Case II. is a coal-field. Collieries are working on the western side only (Figs. 43, 44). The explorer must take all particulars of these depths, inclination of strata, thickness of coal, particulars FIG. 44. Showing section of estate proved by digging and boring. of the strata found in the shafts, faults, if any, extent of workings, water in the mine or in the rocks above, etc. Surface-Indications. Having got all the information that can be obtained at the collieries, the next step is to make a careful examination of the surface, in order to find out what the ground is made of. Sometimes the nature of the ground may be |