152
MODERN STEAM PRACTICE.
heilig cast on each, and turned slightly conical. A small branchpipe is cast on the outer casing at the top for the admission of the
steam, which forms a steam-jacketaround the internal cylinder, andone at the bottom to run off thewater from the condensation ofthe steam in the annular spacebetween the two cylinders; eachof these pipes is fitted with a plugtap. The bed-plate D is a strongcasting, with port E cast on, and isbolted down through the founda-tions with six holding-down bolts.There is a bottom plate F fittedinto and made tight by a rust joint.The cylinder cover G is an opencasting, with separate coveringplate H, and has the stuffing-box Icast on, which is fitted with theusual lantern brass IC, and gland L,for the packing of the piston rod.The piston M is also an open cast-ing, ribbed at the under side, andfitted with a junk ring n, havingbolts with nuts recessed in thebody of the piston; there are twospring packing rings o, of cast iron,accurately turned and made per-fectly steam-tight. The piston rodis let in through the under side,and is turned conical, fitting intoa corresponding hole in the piston,the rod being secured with a cot-ter P at the top. The cylinder isfitted with a ring Q of wood at the bottom, to deaden the shockshould the piston descend so far.
The pump rods are directly attached to the gudgeon at the otherend of the beam by suitable wrought-iron straps, jib, and key. Theend of the pump rod is covered by plates on each side, fastened bycross bolts passing through and through, to prevent the wood strip-