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Chap. 17.]
ered; but in the chain pump, from thirty to fifty have to be renewedwhen worn out. The chain pumps in the British sloop of war Cyanewere taken out when she was captured, and common pumps put intheir place. Recently a change of opinion respecting these pumps hastaken place, for within a few years they have to a limited extent been re-introduced into the navy. In 1837, the Independence was furnished withtwo of them ; and in 1838, the same number were placed in the Ohio :both vessels still retain the orainary pumps.
A description of one of those on board the Independence, which is nowfitting for sea in this harbor, will give a correct idea of them all. See No. 67.
Two copper cylinders, seven inches diameter, and about twenty-twofeet long, extend from the surface of the main gun-deck to the well. Theone in which the chain descends, is continued ten or twelve inches abovethe deck to prevent the water that is raised, from returning through itagain to the well. A horizontal wrought iron shaft is placed between thecylinders and supported by a stout frame on which its journals turn. Onthis shaft, a strong castiron wheel, two feet in diameter, is secured, havingtwelve arms radiating like the spokes of a carriage wheel from the hub. Ä(No. 67) represents two of these arms with a portion of the shaft. A re-cess is formed at the extremities to receive the chain, and prevent it fromslipping off on either side. Figs. 1 and 2, represent the links. They areof copper, seven inches long, one and a half inch wide, and one quarterof an inch thick, and are similar to those in Cole’s pumps. The pallets orpistons are formed on the middle of every alternate link; that is, on thosewhich are made of a single piece. A circular plate about a quarter of aninch thick, is cast (see fig. 1,) of a diameter rather less than the bore ofthe cylinders. Another loose plate of the same dimensions (fig. 3,) hasan opening in its centre to allow it to pass over the link and lay upon theother. Between these, a disk of leather is introduced, i. e. a circularpiece just like fig. 3, but of a diameter equal to the bore of the cylinder.This is first placed on the fixed plate in fig. 1, then fig. 3 is laid over it,and to secure the whole, a key or wedge is driven through a slit in thelink, just above the surface of fig. 3, and thus compresses the leather be-tween them. When the pumps are used, long cranks are applied to eachend of the shaft, so that fifteen or twenty men can be engaged at the sametime in working them. In the Independence, these cranks extend across thedeck, and thereby interrupt the passage way. They should in all publicvessels be arranged, if possible, ‘ fore and aft.’ The arrows show the di-rection of the chain.
The introduction of the chain pump into ships is probably due to theChinese , as they use it in their sea junks; and it is not likely that this ap-plication of it is of recent date among them. B The early missionariesthought that buckets onlv were’employed in raising bilge water fromthe holds. It is not much used we believe in the French navy. In theDictionnaire de Trevoux, it is named the Englüh, pump.
The Chinese chain pump was introduced into the United States byAndre Everard Van Braam, who was several years chief of the DutchEast India Company in China, and who settled in South Carolina at theclose of the revolutionary war. In 1794, he was appointed second in theDutch embassy to Pekin, and in 1796, he returned and settled near Phila-delphia . In his account of the embassy, a translation of which was pub-lished at London in 1798, and dedicated by him to General Washington,and to which we have heretofore referred—he remarks, speaking of the