The selection of localities for boring is very much a matter of chance. Proximity to productive wells is the first desideratum; but this, when attainable, is not always attended with success. The oil does not appear to be spread out, as the rocks lie in horizontal sheets, or if so there are many places where it does not find its way between the strata, and wells near together from which oil is pumped do not always draw upon each other. No doubt the system of crevices and pervious strata through which the oil flows in its subterranean currents, is very irregular and interrupted. The valleys to which the operations are limited are narrow, and are bounded on each side by hills, the summits of which, from 250 to 400 feet above the bottoms, are on the general level of the country. The increased expense that would be incurred in sinking from the upper surface and in afterward raising the oil to this height, as also the uncertainty of finding oil elsewhere than in the valleys, have so far prevented the explorations being extended beyond the creek and river bottoms; but it cannot be long before the capacity of the broad districts between the streams to produce oil is thoroughly tested. At present the most favorable sites are supposed to be near a break in the hills that form the margin of the valley, as where a branch comes into the main stream. An experiment is already undertaken to test the high grounds west of Tidioute branch.

As the bituminous coals are known as a source of hydrocarbon oils, it is natural to suppose that the springs of oil found near the coal region are fed from the coal beds or bituminous shales of the coal formation. But it happens that only a few oil springs of western Pennsylvania have been struck in the coal-measures themselves, and that some of these are sunk into the underlying groups of rock to reach the supplies of oil. The oil districts are in general outside of the coal-field and upon the outcrop of lower formations which pass beneath the coal-measures, the whole having a general conformity of dip. Hence the slope of the strata is toward the coal, and an obstacle is thus presented to the flow of the oil from the coalfield toward its margin; and though under some circumstances the elastic pressure of the carburetted hydrogen gas might force the oil considerable distances from its source, it is hardly to be supposed that this should first find its way down into lower formations

Be

It

and then be carried many miles (30 to 50) and find its outlet in another district, rather than to the surface at some nearer point. The strata of north-western Pennsylvania lie nearly horizontally, their general inclination being toward the south. The highest rock upon the summits of the hills of the oil region is the conglomerate or pebbly rock (the floor of the coal-measures). neath this are series of thin bedded sandstones, slates, and shales, alternating with each other with frequent repetitions. The shales, often of an olive green color, are readily recognized as belonging to the Chemung and Portage groups of the New York geologists—a formation which overspreads this portion of the country, extending in New York two thirds of the way toward Lake Ontario and as far east as Binghamton. is also continued through Ohio, crossing the Ohio river at Portsmouth, and in this state is known as the Waverley series. Under this is a heavy bed of bituminous shale, 200 or 300 feet thick, called in Ohio the black slate and in New York the Hamilton shales. This group contains an immense amount of carbonaceous matter, and oil is often disseminated through it. Sometimes it runs out in springs and finds an outlet by the occasional fissures in the beds. Dr. J. S. Newberry, who has given much attention to this subject, is of opinion that this formation contains sufficient carbonaceous material to be the source of the oil, and that the more porous and open shales and sandstones of higher formations are its reservoirs. Such is the geological formation of the Seneca oil region and of the oil springs of Canada West, which are the districts affording this product most remote from the coal-field. But from whatever source the oil may be derived, its origin is at the best very obscure, and little light can be thrown upon the probability of the supply long enduring the heavy drain made upon it by hundreds of wells worked by powerful steam pumps. But though actual experience alone must determine the extent of the quantities of oil stored up and the period they will last, there is certainly encouragement to be drawn from the never-failing yield of the oil districts of Asia, which for centuries have poured forth without stint their rivers of oil.

The sinking of wells is conducted after the usual method of boring artesian wells. After much uncertain consideration of the chances, a particular spot is selected, more,

perhaps, from the hope of its being the right one than from any very practical grounds for the choice; but as the oil flows only in crevices among the strata, the location is frequently determined-other things being equal-by the prospect of reaching the rock at a few feet from the surface, and thereby avoiding the necessity of sinking an open well or driving pipes through unknown obstacles down to the rock. If the bed rock is found within ten or fifteen feet, the boring is begun at once. The derrick being raised, an elm, hickory, hemlock, or other elastic timber is cut down, some 25 or 30 feet in length. The larger end is fixed in a notch of a tree, or heavy post planted in the ground, and another post is set under it at a distance from the but determined by the elasticity of the timber. The spring of the pole should be sufficient to raise the drill quickly, with its iron connecting rods, weighing often 300 pounds. The rods are suspended from the free end of the pole by a swivel or simple bolt-head, turning freely around. At the commencement of the boring, the rods being very short do not weigh more, including the drill, than 70 or 80 pounds. Two men, therefore, jerk them forcibly down, to increase the momentum of the drill; the spring of the pole immediately raises the drill for the next stroke, while at each blow a man gives it a slight turn so that it may cut a round hole. Several other methods are employed for making the pole spring; by one, which is conveniently worked without employing steam or horse power, a sort of double stirrup is suspended from the pole into which two men place each a foot, and pressing the stirrup suddenly down it immediately springs up again with the drill. This is much used, though some wells are sunk by horse-power machinery, and some by steam engines of four or five horse power.

ed on as the hole deepens-increasing the weight of the tools to about 300 pounds. The use of any additional rods is then dispensed with, and the upper rod is suspended by a rope attached to the spring-pole, and continued above the pole around a pulley and windlass, used to raise the boring tools when it is necessary to draw them out. They are drawn up in this manner at intervals of an hour or two, in order to sharpen and temper the drill, and to make room for the sand pump. This is a thin iron tube, a little more than half the diameter of the hole, with a simple valve at the bottom opening upward. It is lowered by a cord to the bottom of the well, then raised up with a jerk, and suffered to drop again by its own weight. This is repeated quickly eight or ten times; a whirl is thus produced in the water below which stirs up the mud and small pieces of broken stone; as the tube drops, the mud and small stones enter the open valve and are retained when the tube is drawn out.

The jarrers are employed to increase the force of the spring-pole when the drill happens to be wedged in the hole by broken pieces of stone or by other obstructions. They are two rectangular links about 18 inches in length, formed of stout bars of iron, and connecting the upper rods with the lower. When the drill descends to the bottom, the upper link, as it descends, slips down eight or ten inches in the lower link, and when the pole springs up the upper link has the advantage of moving through this space, and thereby giving a sudden upward jerk to the drill rod. The force of this upward jerk is greatly increased by a heavy rod introduced above the upper link, and which, as it moves up, lends its momentum to the stroke.

hard sandstones of quartz pebbles firmly united together, two or three inches sinking in 12 hours may be all the progress practicable. The material brought up is carefully scanned for any oily appearance indicating the proximity of oil, and the well is watched to observe if any carburetted hydrogen gas escapes from it, which is considered a favorable sign.

uncertainties and apprehensions that surround the driving of pipes. At the outset, the cost of four iron pipes and bands long enough to reach a depth of forty feet, is equal to that of a complete set of boring tools with the rods and ropes sufficient to bore half a dozen wells of 300 feet each in depth. There is often great uncertainty of knowing how deep the pipes will have to be driven, and it is impossible to foresee the various obstacles through which they have to go. When the work has gone down successfully 70 or even 100 feet, the lowest pipe is often suddenly broken or takes an oblique direction. The pipes in the ground are then abandoned, and a new set driven in another place, although in several instances pipes reaching 60 feet in depth have been pulled up by a lever and axle, with chains or rods attached to a lewis wedge driven into the bottom pipe.

The pipes are of cast iron, generally ten or twelve feet long, about five inches bore, and the shell full an inch thick. The lower end of the first pipe is not sharpened, but is driven down blunt as it comes from the mould. The pipes are fastened together in the simplest manner possible, by wroughtiron bands, the ends being turned off, leaving a neck somewhat larger than the interior diameter of the bands, to receive them when expanded by heat,

Through common earth or gravel the pipes are forced down by the ordinary process of pile-driving; but when large stones are encountered, or round boulders as large as a man's head, there is great risk of breaking or turning the pipes. As soon, therefore, as the pipes meet with any great resistance the driving is suspended and the drill is applied to break up the stone or to bore a circular hole in it, which is afterward reamed out as large as the interior diameter of the pipes. The driving is then resumed, and in soft shales the pipes are often forced on, crushing down the sides of the hole, and making their way through to the depth of 12 or 15 inches in the rocky stratum.

The cost of boring a well 200 feet deep is generally estimated at from $1000 to $1500. The latter sum includes the cost of all the tools and materials, and also of a small steam engine, a large tank of pine plank, in which the product is collected for the oil and water to separate, and it also allows for such accidents and delays as are common to these operations.

When the oil is struck it often rises up in the well, sometimes flowing over the top, and in several instances it has burst forth in a jet and played like a fountain, throwing the oil mixed with water high up into the air. Such jets have rarely lasted long, and are usually interrupted by discharges of gas, the elasticity of which drives out with violence the fluids mixed with it, as champagne wine is projected from a bottle on removing the cork. Hundreds of barrels of oil have, however, been wasted at some of the wells for want of means to collect it or stop its flow in its sudden first appearance. At Williams' well, half a mile below Titusville, about 100 barrels of oil were collected the first night the oil was reached, and a large quantity besides was lost.

A similar event occurred near Tidioute, the oil rushing up so violently as to knock over the laborer who held the drill and to pass through the derrick and over the trees around. After a time the spouting wells become quiet and the oil settles down, so that it has to be raised by pumping. The pumps are contrived to work at any depth, and by men, or by horse power, or the steam engine. For a time at some of the wells the product has been water alone or water mixed with a little oil; and after pumping several days this has given place to oil with a moderate proportion of water. If the pumping be suspended for a day water accumulates, and it may be several days before this is drawn out and the former yield of oil recovered. The water is generally salt. The flow of oil has rarely if ever been known to fail entirely except by reason of some obstruction in the wells, and in such cases it has usually returned after the hole has been bored out larger or made deeper. The supply is not, however, altogether regular in any of the wells, even after the flow has settled down to a moderate production of 10 or 15 barrels a day. The maximum yield of a well for a considerable time is about 50 barrels a day, and from this the production ranges down to 4 barrels, below which it is considered insufficient to pay expenses.

The oil and water are conducted from the

pumps into the large receiving vats, and after the water has subsided the oil is barrelled for the market. From the upper Oil Creek it is mostly wagoned to the Union Mills station in Erie county, on the Erie and Sunbury railroad; and from Tidioute to Irvine, at the mouth of the Broken Straw, on the same road. But most of the oil along