PMication of the Miner’ s Friend.

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Chap. 8.]

to flow upon the receiver. A pipe attached to the tunnel descended intothe boiler and served the purpose of a gauge cock.

The Operation will be understood from the description of figure No. 193.By turning the handle of Gr steam is admitted into B, and as soon as theair is expelled from the latter, Gr is closed and F opened; the affusion ofcold water (see the figure) quickly condenses the contained vapor, andhence the receiver becomes charged with water by the pressure of theatmosphere through the suction pipe A. F is then shut and Gr opened,when the steam issuing from the boiler displaces the water from the re-ceiver, and having no other way to escape the liquid is driven up the pipeD into the reservoir prepared to receive it. As soon as all the water isexpelled from the receiver, (which was known by applying the hand tothe lower part, for it would be hot) G is shut and F again opened, whenthe Operation is repeated as before.

“ When this engine begins to work [says Switzer] you may raise four ofthe receivers full in one minute, which is fifty two gallons, [less the quan-tities drawn from F for the purposes of condensation]—and at that rate inan hour’s time may be flung up 3120 gallons. The prime cost of suchan engine is about fifty pound, as I myself have had it from the ingeniousauthor’s own mouth. It must be noted that this engine is but a small one,in comparison of many others of this kind that are made for coal-works;but this is sufficient for any reasonable family, and other uses required forit in watering all middling gardens.”

Here is no provision made to replenish the boiler with water exceptthrough the tunnel: hence the working of the machine had to be stopped,and the steam within the boiler allowed to escape, before a fresh supplycould be admitted. Under such circumstances the boilers were veryliable to become injured by the fire when the water became low. Theywere also exposed to destruction from another cause, the force of thesteam; for they had no safety-valves to regulate it, and hence the necessityof the following instructions : “ When you have rais’d water enough, andyou design to leave off working the engine, take away all the fire fromunder the boiler, and open the cock [connected to the tunnel] to let outthe steam, which would otherwise, was it to remain confin’d, perhapshurst the engine ’’

Savery, from his profession, was aware of the want of an improvedmode of draining mines. The influence of the useful arts in enriching anation was then beginning to be understood. A Stimulus was imparted tomanufactures, and the demand for coal and the ores of England rapidlyincreased. As a necessary consequence the depth of the mines increasedalso; and hence proprietors became anxious to possess some device forClearing them of water, and by which the old, inefficient and excessivelyexpensive horse-gins and buckets might be dispensed with. The cost ofdrainage was so great in some mines, that their produce hardly equalledthe cost of working them : in one mine five hundred horses were constantlyemployed. Numerous novel projects had been tried and abandoned :what they were we are not informed, but as Ramseye and Worcester andprobably others had proposed fire machines for the purpose, steam hadprobably been tried in some way or other and had failed. Having greatlyimproved his machine, Savery published an account of it, illustrated withengravings, in a pamphlet entitled The Miner’s Friend ; or a Descriptionof an Engine for Raising Water by Fire, with an Answer to the Objectionsagainst it. London , printed for S. Crouch, 1702. In his address he begsproprietors not to let the failure of other plans prejudice them against thetnal of his. “ Its power [he observes] is in a manner infinite and unlimited,

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