It is very rarely that oil is found on the surface or gushing up by itself without the help of pumps. It is usually met with at a great depth underground, in pockets in which oil and gas are found above water. Thus, in order to detect its presence, it is necessary to make borings. When one reaches a pocket in the neighbourhood of the gas, the latter escapes by the outlet which is offered. If the boring first reaches oil, and if the pressure of gas is sufficient, the oil gushes out and forms a spring. This is what happened in the Caucasus, where certain wells spouted up to a height of eighty metres through the borings made by the prospectors. More often the gas pressure is not sufficient to raise the liquid to the surface, and it is necessary to install pumps driven by steam to empty the pocket. At the time of the boring, when the cylindrical metal drill, driven vertically by a metal cable and held vertical by the derrick (a sort of pyramidal framework of metal), reaches the deposit, the gas which has been accumulating for thousands of years escapes, driving, pushing, sucking up the oil, and making a fountain, a gusher, a sort of artesian well. The oil is led away in metal pipes, vertical till they reach the surface, horizontal to the refineries, ports, or other destinations. Once the well is capped, it is not touched again; it is alone in the desert, and only a metre records its daily output, while hundreds of thousands of men are obliged to work underground to wrest coal from the bowels of the earth by the strength of their arms!