Ships' Pumps.—For a number of years the chain-pump, consisting of a series of metallic dines, regularly arranged ripen it bar chain, each disc acting as a piston, was the only one in use on board laigo ships, ' and it may still he seen in several of our sea-going old line-of-battle Iships, although new chain-putnpa are no longer fitted in her Majesty's service.
Pmnps of various descriptions are in me both in the navy and merchant service—each form having its qualifications. That much is required from them maybe gathered from the fact that :asteamer of mode rate size requires a ton and a quarter of condensing water per hour for each horse power ; and therefore in case of serious leak it is of vital importance to obtain this quantity for injection into the boilers from the hold of the ship by means of the engine itself. Her Majesty's ship Phoenix not long since was saved from foundering in the Bay of Biscay, by thus injecting from the bilge ; but had the injection pipe been unprotected from chips, &e., the ship's pump alone could not have saved her.
The following may be considered to be the necessary qualifications of a ship's pump, namely, it should be I, easy to work ; 2, give a continuous stream of water of the greatest possible quantity ; 3, be not easy to choke; 4, be so simple in construction as to be eAily taken to pieces, and repaired at sea ; 5, the valves should be of durable material; 6, so constructed as in case of choking to admit of the ready removal of the bottom box without withdrawing the piston or pistons.
Among the best pumps in use at sea, may be mentioned Massey's double action ; Dowton's many-pistoned ; Robertson's double action twin pump ; Redpath's pump; Suffield's India rubber valved pump, dm. From-among these, on account of its very peculiar construction,
and from its having been recently tried successfully against several other forms of pumps on board her Majesty's ship Fisgard, we give below an illustration of Redpath's, of Limehouse.
shows its compactness and portability ; fig. 6 bi a section of the working parts. It will be seen that the sunlion pipe is of the same area as the bottom valve, so that considerable friction and therefore labour are thus saved ; and the bottom valve, like the upper valve, requires uo fixing : both valves being made wholly of metal they drop into their places—it is therefore scarcely possible for them to get out of order.
The whole is exceedingly simple, and whereas at the trial in the Fisgard the other pumps occupied about seven minutes in taking apart and being replaced into working order; Redpath's was done in about half a minute (a valuable qualification in a leaky ship). This pump has no leather buckets nor bottom boxes, but the bottom valve is so placed that should any accumulation of sand, tar, oakum, chips, or shingle occur, if they are too large for the pumps to deliver, it is only the work of a few seconds to lift the valves in order to free them. Nearly 1000 of these pumps are afloat iu British ships, and the simplicity of its action has obtained for it also a large sale in the American and other navies.