156

Chain Pumps

[Book 1.

distance between these bolts is such that the pistons fall in betweenthem, and are carried round by them. Soraetimes however, the linkshave hooks, which take hold of the bolts. A lower wheel is nowdispensed with, and the end of the pump slightly curved towards thedescending chain, to facilitate the entrance of the pistons. These ma-chines are generally worked in ships of war by means of a long crankattached to the axle, at which a number of men can Work. In some ves-sels they are moved by a capstan. a The pump cylinders are of iron, andsometimes of brass, the latter being inclosed within and protected bywooden ones.

No. 67. Chain Pump in the U. S. Ship Independence.

Bill

For the following facts connected with the use of the chain pump inthe United States Navy , we are indebted to Mr. Hart, Naval Constructorin the New-York Navy Yard. The first United States ship of war,which had one, was the ‘ Boston, ’ built at Boston , in 1799. Mr. Hart’sfather made the pump. The chain was formed of common ox chains,and the wheel which carried it was of wood, having forked pieces of irondriven into its periphery, between which the chain was received : the cyl-inders were common pump logs of six inches bore. This imperfect ma-chine was replaced the following year, by one formed after a Frenckmodel, the chain and cylinders being of copper. In 1802, the Frigate Con-stitution had two similar ones placed in her ; and about the same time,they were adopted in other public vessels; but in the course of a fewyears were discontinued generally, either from the prejudice of tbeseamen, or from the increased labor and expense of repairing the pis-tons. In ordinary pumps, a single box or piston only, has to be re-leath-

a The vessels of the exploring expedition sent out by the British admiralty, under thecommand of Capt. Owen, had their chain pumps fitted to work by the capstan, underthe impression that it was a more economical mode than the crank, of applying per-sonal labor. ‘ Narrative of Voyages to explore the shores of Africa, Arabia and Mada-gascar, in 1821.’ Vol i, p. 14. N.York Ed. 1833.