Page:International Library of Technology, Volume 93.djvu/95

 in fact nearly always, the best wells are in rows. Such rows are known as belts. These rows are not usually straight, but take on a gentle curve, the curve following a crevice in the

rock, as a b or c d, Fig. 1. This crevice is usually filled with various deposits, generally sand and loose rock, which contain the oil. In the vertical crevice a b, the line on which oil may be found is very narrow. The crevice cd gives a wider

oil line, but the wells most distant from the line cd must be drilled deeper. It can readily be seen that a well sunk at h would be dry, no oil being found, while a well at i would strike oil at a great depth.