196

MODERN STEAM PRACTICE.

H-piece. Around the seating is wrapped a strip of coarse flannelor baize, which makes the joint when the seating is forced into itsplace. Above the door of the H-piece is placed the door piece,which contains the delivery valve, which is fixed in the same way asthe suction valve. On the door piece the pumps or rising main, in9-feet lengths, are placed. It is usual to place a wind bore directlyunder the H-piece, leading into a cistern from which the pump takesits water, but in the example under notice a much better arrange-ment has been adopted. The cistern is placed just above thesuction valve, so that the water may more readily follow up theplunger, and thereby cause the pump to be ‘charged solid.’ It isof very great importance that no vacant space whatever should beleft in the pumps at the termination of the indoor stroke of theengine, for if there be a space not occupied with water, then a shockensues, and the engine works as if working in ‘ fork,’ or as if thepumps were taking air. A 6-inch branch and blank cover is pro-vided in the U-piece under the H-piece, for the convenience ofgetting out anything which may accidentally drop into it. A blankend and ‘matching’ piece is put on to the H-piece under the polecase, which takes its bearing on the timber bearers below. Themain rods are of Memel timber, perfectly sound and straight, with-out knots or faults; for the first 50 fathoms they are 18 inchessquare, for the next 40 fathoms 16 inches square, and for the last30 fathoms 14 inches square. The rods are obtained as long aspossible, and are jointed by means of‘strapping plates,’ bolts, andnuts. The timber is sometimes cut in the form of a splice, andmade to form a lap joint, but in this case the rods are all butt-jointed, the strapping plates are first firmly secured to the piece tobe attached, and then the piece is put in its place on the main rods,the joint being brought up tight by powerful lifting jacks. Themain rods are kept in a line by means of wood guides fixed atintervals. The plungers are cast with a plain core through them,and a little longer than is necessary for the stroke; the castingshould be entirely free from Specks—it is usual to cast them on theside, but we prefer to have them cast on end. The plunger is‘stocked’ on the mine; a piece of Memel timber, square in section,and equal in diameter to the plunger, is obtained, about 12 feetor 14 feet longer than the ‘ pole.’ For a portion of its length equalto that of the pole it is rounded down, and the pole is then forcedon to it. When stocked it is fixed by means of Staples and glands