He assumes that in what is considered a good producing district the amount of petroleum which can be obtained from a cubic foot of rock would not be more than a gallon, and that the average thickness of the oil-bearing rock would not exceed 5 ft.
Linseed and other oil-bearing grains are also important articles of commerce, as well as wool and butter.
The stratified rocks of this system include marine limestones, shales and sandstones; estuarine, lagoonal and fresh-water shales, sandstones and marls with beds of coal, oil-bearing rocks, gypsum and salt.
A variety of oil-bearing plants and green fodder, as also cotton, hemp, flax and poppies, are grown.
It is either set in the first instance at some distance from the engine and well, or is subsequently removed sufficiently far away before the drill enters the oil-bearing formation, and until the oil and gas are under control, in order to minimize the risk of fire.