tion of the portion necessarily occupied in the drilling operations. If the district is already "proved," the lessor frequently receives a cash payment of $100 per acre, together with one-eighth of the oil pro duced. Drilling in California. The wells in Pico Cañon (California) range in depth from 700 to 2,000 feet, and are usually commenced with a 10- or 12-inch bore. It is the aim of the driller to carry a 5 hole to the principal oil-bearing formation, but occasionally it is found necessary to reduce the final diameter to 3 inches. All the wells are cased to prevent caving, but some have no provision to exclude water. The length of time occupied in drilling to a depth of, say, 1,500 feet, varies from four to five months. The wells in this district are not torpedoed. Casing. The casing, each string of which extends from the mouth of the well, is made up in lengths of 17 to 20 feet, screwed together. The arrangement represented in Fig. 38 is employed for raising and lower- As the hole is never drilled quite true, and an allowance has also to be made for the larger diameter of the sockets connecting the lengths of the casing, a 13-inch bit is used for drilling a hole which is to receive 10-inch casing, a 10-inch bit for 7g casing, and a 7-inch bit for 5 casing. Fig. 38. Danger of Fire.-It has been already mentioned that the boiler supplying steam to the drilling engine is placed at some distance, in order to reduce the risk of fire, but notwithstanding the adoption of this precaution, many lives have been lost and much property destroyed through the ignition, at the boiler fire, of gas or oil spray from the well. The outflow, when the oil-bearing formation is penetrated by the drill, not infrequently takes place with such violence that the drilling tools are projected from the well, and flowing wells, which have become accidentally ignited, have in some instances continued burning for a long time, all attempts to extinguish the flame having failed. The author has given particulars of such cases, and described the appearance presented by burning oil and gas wells in his "Cantor Lectures on Petroleum." Yield of Wells-Inducing Flow-Pumping. The yield of the wells varies within very wide limits, and the relative importance of the different producing districts is also constantly changing. According to Stowell's Petroleum Reporter, there were, in 1885, no less than 23,586 productive wells in the United States. Many of these were flowing wells, but most of them required pumping. In the Washington field, the cost of drilling is so great that no well can be considered to pay unless the yield amounts to about 100 barrels daily, but in other districts a much smaller yield is remunerative. A flow of oil may often be induced in a well which would otherwise require to be pumped, by preventing the escape of the gas which issues with the oil, and causing its pressure to raise the oil. As this pressure only accumulates gradually, the flow thus produced is usually intermittent. The device employed for this purpose is known as the water packer, and consists in its simplest form of an indiarubber ring, which is applied between the tubing and the well casing, so that upon compression it makes a tight joint. The gas thus confined in the oil-chamber forces the oil up the tubing. For pumping a well, a valved "working barrel," with valved sucker (Fig. 39), is attached to the lower end of the tubing, a perforated "anchor" being placed below. The sucker carries a series of three or four leather cups, which are pressed against the side of the working barrel by the weight of the column of oil. The sucker is connected by a string of sucker-rods with the walking beam. Fig. 40 shows an arrangement employed for working the pumps of a number of adjacent wells from one engine. The ends of the axle of the driving wheel, a, are cranked so as to drive the "pitmen," b. These communicate an oscillating motion to a wheel, c, to which they are connected by ball and socket joints, ani through the medium of the rods, d, connected to the wheel, the necessary motion is imparted to the sucker rods at the various wells. Fig. 39. The pump rods are sometimes formed of iron, but are usually of white ash or hickory of circular or octagonal section. They are generally about 25 ft. long and 1 in. in diameter, and are connected together by male and female screws on iron ferrules. There is usually fixed above the sucker a short iron valve rod, with a rivet catcher (Fig. 41), to prevent damage to the pump from the dropping of rivets from the pump rods. O 0 0 0 Fig. 41. Fig. 40. Fig. 42 shows a "sucker-rod elevator," which is used with a line for the purpose of raising the pump rods. It is laid upon the derrick floor, and the neck of the pump rod being inserted in a slot, a, is firmly held as soon as the cable clinch is pulled, as it becomes locked by a tail, b, descending into the end of the slot. The length of time during which a well continues to yield in paying quantities varies considerably, but has C Fig. 42. been estimated as averaging about five years in the oil fields of the United States. It is usual to remove the casing from exhausted wells for use in new wells, and as the flow of water from the water-bearing strata into the oil sands has been found to materially reduce the yield of adjacent wells, the Pennsylvanian Legislature has enacted that such abandoned and uncased wells shall be "plugged," by filling them with sand. The arrangement employed for separating the gas and oil obtained from a pumped well is shown in Fig. 43. The oil is pumped into a gas tank" near the middle of the derrick, and having there become separated from the gas, flows into a larger tank shown to the right of the figure, while the gas passes away and is utilised as fuel, or for lighting purposes. Both oil and water are pumped at the same time, the rods of the water pump and oil pump being connected to the walking beam. The water is delivered into a separate tank shown to the left of the figure. In the case of flowing wells, the oil and gas flow together into the gas tank, and there separate as already described. Torpedoing Wells.-On the completion of the drilling, or when the production is found to decrease, it is usual to "torpedo" the well to increase the flow. This process was patented in 1862 by Colonel Roberts, who believed, with many others, that the oil was contained in crevices in the rock, which might not have been tapped by the bore-hole. He, therefore, proposed the use of nitroglycerine, gunpowder, or other explosive, to break up the rock at the bottom of the well, so that these rich "pockets" might be brought into communication with the well. At first Roberts was unable to try his invention, as producers were afraid of injury being done to their wells, but in 1865 he was allowed to experiment upon the "Ladies' " well near Titusville, and obtained a favourable result. In December of the following year, he exploded a torpedo in a "dry hole" (the "Woodlin" well) on the Blood farm, and obtained a production of 20 barrels daily, which was increased to 80 barrels by the explosion of a second torpedo. The most striking result, however, was in the case of the "Armstrong No. 1" well, of Thorn Creek, Warren County, which, in 1884, after having been considered a "dry hole," was converted, by a heavy torpedo explosion, into a rich producer. In the first hour after the explosion, a 500barrel reservoir is said to have been filled. In shallow wells of only a few hundred feet in depth, gunpowder is found to be more effective than nitroglycerine, as the latter does little beyond expelling the air or water from the well, but in the deeper wells of Pennsylvania, nitroglycerine is exclusively employed. The amount of explosive used has been increased from the original 4 to 6 quarts, to 60, 80, 100, and even 200 quarts. It is placed in tin canisters of about 3 to 5 inches in diameter, and about 10 feet in length. The canisters have conical bottoms, and fit one in the other, as shown on the right in Fig. 44. They are separately filled with nitroglycerine, and are lowered to the bottom of the well, one after the other, by a cord wound upon a reel, until the required number have been inserted. Formerly, the upper end of the highest canister was fitted with a "firing-head," consisting, as shown, of a circular plate of iron, slightly |