Total time of drilling, about 47 days-66 days from time drilling began, to completion of well. Average progress, about 36 feet per day. Best twenty-four hours' work, 101 feet. cased at 435 feet. Torpedoed on completion, when it gave a heavy Well drilled dry; flow of oil for a short time, and afterwards yielded about 35 barrels per day. In this case, the well was drilled to a further depth of 48 feet after the oil was struck, and this procedure is general, in order that a considerable surface of the oil-bearing formation may be exposed in the well. Oil Saver.-As the oil frequently flows from the well mouth during this extension of the depth, an "oil saver" (Fig. 37) is employed. This device consists of a cap fitted to the top of the well casing, and having a lateral pipe communicating with a reservoir for the oil. The cable is bound with cord to minimise friction, and passes through a tube, d, cE which works in a gland in a ring, b, secured by screws, c. For clearing out débris, a ladle, working through a ring, ƒ, is employed. The Evolution of the present Drilling System.— An oil well consists of three sections-the first formed of surface clays and gravels, the second of stratified rocks containing water, and the third of stratified rocks, including the "oil-sands," usually free from water. The conductor, already described, passes through the first of these divisions, and "casing" is used in the second to prevent percolation of water into the oilbearing portion. Plate XI. represents longitudinal and cross-sections of Fig. 37. C typical wells in 1861, 1868, and 1878, and indicates the main improvements effected from time to time. In 1868, the wooden conductor previously used was replaced by cast-iron drive-pipe, and a 31-inch casing was fitted permanently in the wells down to the lower portion of the water-bearing strata. The end of the casing was packed either with the "seed-bag" or with a leather cup which was forced open against the sides of the well by the water pressure. Two-inch tubing, suspended from the casing, passed nearly to the bottom of the well. As the casing was 31 inches, and the uncased part below was 5 inches in diameter, it was difficult to introduce fishing tools, and if the well required deepening, only a 3-inch bit could be employed. Important improvements in the system of drilling and casing are shown in the drawing of the well of 1878. An 8-inch wrought-iron drive-pipe, terminating in a steel shoe, is driven to the bed-rock, and a 77-inch hole is drilled below it to the base of the lowest water-bearing stratum. The bore is there reduced to 5ğ-inch and a bevelled shoulder being made in the rock, a 5-inch casing, having a collar to fit water-tight on the bevelled shoulder, is inserted. The well is then completed with a 5-inch bit. As the water is shut off before the portion of the well below the water-bearing strata is bored, the remainder of the drilling is conducted with only sufficient water in the well to admit of sand pumping. The drill is thus allowed to fall freely, instead of being partly upheld by the buoyancy of the water, as in the earlier wells. The depth of the wells increased from 436 feet in 1861, to 1,606 feet in 1878, and has still further increased since that time. A well drilled to the Clinton limestone at Mansfield, Ohio, has reached a depth of 3,594 feet, and it is stated that an unproductive well, or "dry hole," has been carried to a depth of 4,303 feet in the Washington field. The difficulty of drilling at these depths is very great, and highly-skilled operators are required for the work. In the Washington field, where the wells are very deep-averaging about 2,400 feet-there are wells which, in consequence of repeated mishaps, have been abandoned with three strings of tools in them. Drilling in the Washington Field.-In this field, the average time occupied in drilling a well is four months, and the cost averages $8,000, as against $2,500 to $3,000 in the Bradford field. In the former, the driller is paid at the rate of $1.75 to $2.00 per foot, while in the latter, the usual rate of payment is 45 to 60 cents per foot. The drilling contractor provides the labour, the cable, the tools, and the coal, while the well owner provides the derrick (costing about $500), a boiler of 25 H.P. (about $500), an engine of 20 H.P. (about $200), and the necessary connections (about $100). The contractor pays the driller $4 per day, and the tool dresser $34, so that, allowing for the day and night shifts, wages amount to $15 per day of twenty-four hours. Occasionally the contractor provides the whole outfit, with the exception of the derrick. An oil lease in the Washington field is usually for a period of five years, or as much longer as production continues, and generally contains a covenant that operations shall be commenced in one or two years, or that a stated rental per acre shall be paid. The land owner retains all rights over the surface of the land, with the excep |