Clumsy and comparatively ineffective though the engine was in this form, it was, nevertheless, found of some use in pumping water from mines. In 1711 Newcomen and Calley made proposals to the owners of a colliery at Griff, in Warwickshire, to drain the water from their pits, which until then had been drained by the labour of horses; but, the owners not believing in the practicability of the scheme, their offer was declined. In the following year, however, they succeeded in obtaining a contract with Mr. Back, for drawing the water from a mine belonging to him near Wolverhampton. The place where the engine was to be erected being near to Birmingham, the ironwork, the pump-valves, clacks, and buckets, were for the most part made there, and removed to the mine, where they were fitted together. Newcomen had great difficulty at first in making the engine go; but after many laborious attempts he at last partially succeeded. It was found, however, that the new method of cooling the cylinder by surrounding it with cold water did not work so well in practice as had been expected. The vacuum produced was very imperfect, and the action of the engine was both very slow and very irregular. While the engine was still in its trial state, a curious accident occurred which led to another change in the mode of condensation, and proved of essential importance in establishing Newcomen’s engine as a practicable working power. The accident was this: in order to keep the cylinder as free from air as possible, great pains were taken to prevent it passing down by the side of the piston, which was carefully wrapped with cloth or leather; and, still further to keep the cylinder air-tight, a quantity of water was kept constantly laying on the upper side of the piston. At one of the early trials the inventors were surprised to see the engine make several strokes in unusually quick succession; and on searching for the cause, they found it to consist in _a hole in the piston_, which had let the cold water in a jet into the inside of the cylinder, and thereby produced a rapid vacuum by the condensation of the contained steam. A new light suddenly broke upon Newcomen. The idea of condensing by injection of cold water directly into the cylinder, instead of applying it on the outside, at once occurred to him; and he proceeded to embody the expedient which had thus been accidentally suggested, as part of his machine. The result was the addition of the injection-pipe, through which, when the piston was raised and the cylinder was full of steam, a jet of cold water was thrown in, and the steam being suddenly condensed, the piston was at once driven down by the pressure of the atmosphere.