In another and still simpler little machine,[24] which he erected at Kensington (Fig. 12), the same general plan was adopted, combining a suction-pipe, _A_, 16 feet long and 3 inches in diameter; a single receiver, _B_, capable of containing 13 gallons; a boiler, _C_, of about 40 gallons capacity; a forcing-pipe, _D_, 42 feet high, with the connecting pipe and cocks, _E F G_; and the method of operation was as already described, except that _surface-condensation_ was employed, the cock, _F_, being arranged to shower water from the rising main over the receiver, as shown. Of the first engine Switzer says: "I have heard him say myself, that the very first time he played, it was in a potter's house at Lambeth, where, though it was a small engine, yet it (the water) forced its way through the roof, and struck off the tiles in a manner that surprised all the spectators." [24] Bradley, "New Improvements of Planting and Gardening." Switzer, "Hydrostatics," 1729. [Illustration: FIG. 12.--Savery's Engine, 1698.] The Kensington engine cost £50, and raised 3,000 gallons per hour, filling the receiver four times a minute, and required a bushel of coal per day. Switzer remarks: "It must be noted that this engine is but a small one in comparison with many others that are made for coal-works; but this is sufficient for any reasonable family, and other uses required of it in watering all middling gardens." He cautions the operator: "When you have raised water enough, and you design to leave off working the engine, take away all the fire from under the boiler, and open the cock (connected to the funnel) to let out the steam, which would otherwise, were it to remain confined, perhaps burst the engine." With the intention of making his invention more generally known, and hoping to introduce it as a pumping-engine in the mining districts of Cornwall, Savery wrote a prospectus for general circulation, which contains the earliest account of the later and more effective form of engine. He entitled his pamphlet "The Miner's Friend; or, A Description of an Engine to raise Water by Fire described, and the Manner of fixing it in Mines, with an Account of the several Uses it is applicable to, and an Answer to the Objections against it." It was printed in London in 1702, for S. Crouch, and was distributed among the proprietors and managers of mines, who were then finding the flow of water at depths so great as, in some cases, to bar further progress. In many cases, the cost of drainage left no satisfactory margin of profit. In one mine, 500 horses were employed raising water, by the then usual method of using horse-gins and buckets. The approval of the King and of the Royal Society, and the countenance of the mine-adventurers of England, were acknowledged by the author, who addressed his pamphlet to them.