The crude is pumped into small flow tanks, and from there run either to a pipe line station or to a “tank farm.” The problem of saving the flow of gushing wells at one time presented serious difficulties; and one of the most valuable of the early inventions was the clay underground tank. The petroleum is directed into a sump-hole lined (wherever possible) with clay, which, because of its close texture, makes an absolutely leakage proof reservoir. From the sump-hole it is pumped to the tanks, but this is usually but a temporary shift. When the gushing process ceases, pumps are installed and direct pipe connection with the storage tanks is established. The modern pump which lifts the oil from the oil-bearing strata to the surface is a very powerful mechanism. One of these will handle a column of oil as high as four thousand feet, and deliver it into pipes. As has been mentioned in alluding to the California seacoast fields, the intervening ocean itself constitutes no obstacle to operations. Not infrequently the walking beam, used in the drilling, is brought into commission for pumping purposes. It is rather a cumbersome system but has this advantage, that it enables the operator to begin production immediately and realize cash for his output. In what is known as the field tank, situated adjacent to the derricks and pumps, the oil operator deposits his daily production, which is later pumped to the “tank farm” for shipment. The capacity of a tank is known to a gallon. So many inches or feet of petroleum in a tank represent so many barrels. The gauger drops a steel tape into the oil until it touches bottom, and the location of the oil showing on this steel is the measure of the contents. Then the valves are opened and a portion of the contents flows away to the pump station or “tank farm.” A second measurement is taken, and the difference between the first and second measurement reveals the quantity of oil drawn off. The gauger then issues to the producer a credit certificate or “run ticket” representing the quantity of the crude received at that particular time. There are other complications, however, before the oil reaches the market. If the wells are gaseous in any considerable degree, the oil must pass through a gas separator before it enters the tanks. The gauger must measure and draw off any water present, which, owing to the proverbial incompatability of oil and water, is not difficult, and in calculating the amount of the credit slip he sees to it that no water is inadvertently paid for.