Chap. 8.]

Its excellent features—Coupling Screws.

459

Between these valves two short curved tubes connect the bottoms of thereceivers I M with the branches, as represented, and two other bent tubes,P Q,, unite the top of the receivers with the boiler H. On the top of thisboiler, and forming a part of it, is a stout round plate, having two openingsof the same size as the bore of the tubes last mentioned. In these open-ings the two steam tubes P Q, terminate. Between the openings, andon the under side of the plate, is a moveable disk, which by a short armis connected to an axle and moved by the long lever shown on the top ofthe boiler; so that by moving this lever the disk can be made to closeeither opening, so as to admit or exclude steam from the receivers, andanswering every purpose of a three-way cock. It is made somewhat onthe plan of the one in No. 189, page 421. The face of the disk is groundsmooth, so as to fit close to the under side of the plate, against which it ispressed by the steam. The perpendicular axle by which the disk is turnedpasses through the plate, and the opening is made tight by a stuffing box.(The plate and moveable disk are represented in the small figure at the top,one of the openings being covered by the disk and the other exposed.)A small cistern, U, is placed over the receivers, and kept supplied withcold water from the forcing pipe by means of a ball cock, viz. a cockthat is opened and shut by a ball floating in the cistern. From the bottomof this cistern a short pipe, T, proceeds; and to it is connected, by a swiveljoint or stuffing box, another one at right angles. This pipe furnisheswater to condense the steam in the receivers, over both of which it can bemoved by the rod attached to the plug of the cock as shown in the figure.The upper cistern denotes the place where the water raised by the engineis to be discharged.

A communication is made between the boilers by a siphon or bent tube,R, whose legs extend nearly to the bottom of the boilers. In the legwithin the small boiler is a valve opening upwards, which permits thewater of G- to pass into H, but prevents any returning from the latter.When the attendant wishes to inject into H a fresh supply of water, heincreases the little fire kept up under the boiler G, (which is always keptsupplied with water by the pipe S,) and as soon as the liquid boils andthe force of the steam exceeds that in H, the contents of G, both steamand hot water, are forced through the valve; and thus H is kept suppliedwithout the action of the machine being stopped. The cock on the pipeS is then opened, the small boiler again charged, and the water becomesgradually heated ; so that by the time it is wanted in the other boiler, asmall addition to the fuel quickly raises its temperature, and it is againforced in as before.

The quantity of water in the boilers was ascertained by gauge cocks.These were inserted at the top, (see figure) and pipes soldered to themdescended to different depths.' The principal boiler had two of these, theother but one.

The general arrangement of this engine and the adaptation of its variousparts to each other are admirable, and could hardly be improved. Theobviously good workmanship—the improved form of the receivers—andthe connection of these with the boilers and pipes, and the latter with eachother, by coupling screws, thus securing easy access to the valves—arehighly creditable to Savery and the workmen he employed. Every partwas made of the best materials. The cocks, coupling screws, regulator,valves, and all the pipes immediately connected with them, were of brass;while the boilers, receivers and suction pipes were of “ the best hammeredcopper, of sufficient thickness to sustain the force of the working engine :in short, [continues the inventor] the engine is so naturally adapted to