Page:Walker (1888) The Severn Tunnel.djvu/296

Rh These plates are bolted on to a cast-iron head and bottom-piece, the latter also carrying the air-pump, which is of the ordinary type.

The whole is contained in a large cast-iron cistern, supplied with a continuous stream of cold water by a pump worked from the main pump-rod.

The exhaust steam passes from the cylinder through the tubes, and being condensed by the action of the cold water without, collects at the bottom of the condenser, and is pumped back into the boilers.

The pumps are of two kinds, three being of the bucket-lift type and three of the plunger, all with a stroke of 9 feet.

The bucket-lift has a working barrel of 35 inches internal diameter, with a gun-metal lining throughout, and fitted with a gun-metal bucket, carrying Husband’s patent four-beat valve on same. The bucket is made extra deep, and without packing.

It is connected with cotter and cap connections to the wrought-iron rods 6½ inches diameter.

The bottom valve is also of gun-metal of the four-beat type, seated in a strong cast-iron valve-box, and secured thereto by a suitable steel crosshead. A large circular door is provided for the ready removal of valves. The valve-box rests on a strong cast-iron windbore, having from two to three thousand 1¼ inch holes in it, the whole being supported by, and secured to, massive foundation-plates at the bottom of well.

The rising-main is of cast-iron of 39 inches diameter, in sections 9 feet long, having a wrought-iron collar-launder at the head for the delivery of the water into the culverts. The pump-head is provided with a suitable guide for the pump-rods.

Each plunger-lift has a plunger-pole, 35 inches diameter, accurately turned, and working into a pole-case, having a suitable stuffing-box with gun-metal bushings.

This plunger-pole is surmounted with a large load-box, which is filled with cast-iron weights, which, together with the rods, balance the column of water in the rising