WELLS AND Wells are excasations for water or other substances such as petroleum, gas or salt; well-sinking is, therefore, the operation by which deep holes of comparatively small diameter are sunk into the earth. Similar holes are drilled in search of coal, iron ore and other minerals, and, al though in this case water is not the object in view, yet work of this character may properly he regarded as well-sinking. The process of well-sinking usually implies also the casing of the well either to guard against the choking of the well or to shut out liquids from all strata except that which the well is designed to tap. Wells are variously classified accord ing to the method of sinking, a dug, bored, driven, drilled and jetted; a curb, case or tube wells according to the manner of lining them; as open, shallow or deep; and as artesian, flowing, non-flowing and pumping.
As regards the dug well, the method em ployed is to excavate it with pick, shovel or drill, shoring the sides with stout planking as the excavation proceeds.
Boring or drilling, however, differs essen tially from digging in that all the operations are conducted from the surface, the ho!c being from 3 to 27 inches or more in diameter. Two distinct nothods of well-sinking arc commonly included under the terms well-drilling and well boring, siz., the grinding with pressure, by which a hole is made, and the pounding or shattering of rocks by a heavy chisel-pointed bar. The two methods and the machinery adapted to their application are represented in their highest development on the one hand by the diamond-drill and on the other by the rope-drill or ordinary oil-well apparatus so well known in America. The first cuts or bores a hole. either cslindrical or annular, in any desired direction; the other pounds and shatters a h. it by its own weight, descending vertically. 7 he pounding or percussion dnll is in common use for sinking deep wells either for fresh water, trine, petroleum or gas, while the diamond drill is only occasionally used for this purpose. finding the greatest utility in ex ploring the harder, inclined rocks for coal, iron ore, the precious metals, etc. The per cussion drill consists of an iron bar tipped with steel drawn to a blunt cutting edge, which is raised repeatedly a few inches and dropped upon a rock, thereby cutting a depression. By slightly turning the bar each time it is raised and causing the chisel edge to strike across the mark kft by the preceding blow the depression gradually becomes a nearly circular hole. The
hole gradually deepens until the powdered rock prevents further progress. Water is now put into the hole and makes a soft mud of the rock dust, which is now drawn out, and the drilling is resumed. To manipulate long, heavy tools required for a deep well the latter are usually suspended from ropes. More or less complicated machinery is employed but the essential parts of the operation are as described above—raising and letting fall the drill and withdrawing the pulverized rock at regular in tervals. The greater number of deep wells are now drilled by steam or gasoline power, while hand and horsepower are used for shallow wells in localities where labor is cheap.
Wells varying from 1,000 to 2,000 feet and over in depth are being drilled in the United States at the rate of about 500 a month. These are mainly in the oil and gas regions of the coun try, such as Indiana, Ohio and Pennsylvania. The machinery in common use, whether for water or oil, has been developed and brought to its present high degree of perfection in these oil-filds, where certain standard sizes and pat terns have been adopted after years of trial. The most prominent object about a deep-drilling well is the derrick or rig, a framework tower 20 feet square at bottom, tapering to four feet at top, and usually 72 to 100 feet high. This tower is for the purpose of carrying two pul leys, the crown pulley in the centre and the block through which the sand-dine runs. Over the crown pulley runs the cable by which the drilling tools are suspended and raised or low ered, while the sand-line is a smaller rope and to draw out the sand-pump or bailer, by which the hole is cleaned at short intervals during the drilling. At one side of the rig are the bull wheels or windlass upon which the cable is wound, and at the other the walking-beam, a heavy timber 20 feet long hung in the centre so that it can oscillate up and down. One end comes directly over the hole, and the other can be attached by a pitman to a crank driven by the band-wheel, which in turn is belted to the engine. This large band-wheel can also be made to run the sand-reel or long windlass carrying the sand-line, one end of the reel being drawn when in use by a powerful lever against the band-wheel.