MODERN STEAM PRACTICE.

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being placed on the pipe in the first instance, the lioop is thenslipped into its place, and the gland pressed down on the hemppacking in the usual manner; the other end of the pipe is securedby a flange bolted to the cylinder. There are also other forms ofexpansion joints. Some have hollow discs formed on the body ofthe pipe, with end flanges for securing the pipe to the cylinder andcondenser, thus forming a rigid stay between the two, but havingthe power of expanding by compressing the flat discs, and con-tracting when the strain is off by opening the disc plates. Weprefer, however, the usual mode with stuffing box and gland. ThePosition of the condensing chambers varies, and depends greatly onthe location of the air pumps. When these are placed together, oneon each side of the middle frame for carrying the cranked shaft,the condensers are then generally in a line with the outer frames, orfore and aft of the outer lines of the cylinders. In return connect-ing-rod engines, with the discharge chambers placed between thecentre lines of the cylinders, and in similar arrangements of airpumps, the condensing chamber and discharge chambers are bothplaced between the centre lines of cylinders; this plan necessitatesthe cylinders to be placed further apart from centre to centre—thatis to say, when the air pumps are located at the side of the motionor guide bars for the crosshead. Sometimes the air pumps arearranged underneath the motion bars, having the discharge chamberat the middle between them, and the condensing chambers on eachside; while, in other examples, with one air pump on the outsideof each outer frame, fore and aft, the condensing chamber anddischarge chamber are cast together immediately over the air pump.In direct-acting single piston-rod and double-trunk engines, theair pumps are always placed one on each side of the centre frame,having the condensing and discharge chambers located immediatelyabove them; while in plunger air pumps with single-acting arrange-ments for foot and head valves, suited for single trunk and returnconnecting-rod engines, the condensing and discharge chambersare placed immediately over the pumps.

The general arrangement of all these forms of condensers,exhaust, discharge, and injection pipes, air pumps, with foot andhead valves, &c., cast in one or more Castings, is as follows. Whenthe air pumps are arranged one on each side of the middle frame,there are generally two separate Castings, all the fittings for whichare kept quite independent. The air pump in all the examples