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[Book II.
the wreck of some vessels in which Germanicus and his legions saileddown the Amisia into the German ocean: “the billows broke over themwith such violence, that all the pumps at Work could not discharge thewater.” [B. ii, 23. Murphy’s Translation.]
Martial, the Roman poet, speaks of the antlia as a machine ‘to draw upwater according to Ainsworth, ‘a pump.’ Kircher figur.es and descnbesthe old wooden pump as the antlia. [Mundus Subterraneus, tom. ii, 196.]The Romans appear to have employed it exclusively or nearly so intheirnavy; and even in that of the Greeks it is not probable that thescrew was extensively adopted, on account of its not being so well adap-ted for ships as the other. Of this the former people seem to have beenconvinced; they preferred the pump and all modern nations have con-firmed their judgment. Had they used the screw to any extent itwould have been continued in European vessels after the fall of the Em-pire, when most of their arts and eustoms were naturally and necessarilycontinued—their ship pumps as well as their ships. But as the atmos-pheric pump only has so come down, we infer that the machine now com-monly used to discharge water from the holds of our vessels is identical,or nearly so, with that employed by Roman sailors of old,
The oldest modification of the ship pump appears to have been thatformerly known as the ‘bilge’ or ‘ burr’ pump; and it was the simplest,for it had but one distinct valve, viz. ‘ the lower box,’ as the one whichretains the water in a pump is sometimes named. This pump kept itsplace in ships tili the last Century, and may yet occasionally be met within those of Europe . It was of'ten worked without a lever, but its pecu-liarity consisted principally in the construction of the piston or sucker.“It differed from the ordinary pump “in that it hath a staff, six, seven oreight foot long, with a bur of wood whereunto the leather is nailed, andthis serves instead of a box; so two men Standing over the pump, thrustdown this staff, to the middle whereof is fastened a rope for six, eight orten to hale by, and so they pull it up and down.” This account publishednearly 200 years ago, might be sufficiently descriptive then, when thepump was in common use, but few persons could no\y realize from it acorrect idea of the Substitute for the ordinary sucker. It is however ra-ther more explanatory than the accounts given in later works. In some ithas been described as “ a long staff with a burr at the end to pump up thebilge water.” Here the burr only is mentioned, not the leather, and theidea imparted is that of a solid' piston, such as are used in forcing pumps.
The sucker of the bilge pump consists of a hollow cone or truncated coneof strong leather, the base being eq.ual in diameter to that of the pumpchamber or cylinder. It is inverted and nailed to the lower end of therod. The lower edge of the leather resting against the burr. Whenthrust down it collapses and permits the water to pass between it and thesides of the chamber, and when its motion is reversed, the weight of theliquid column above it, presses it out again. To prevent the cone fromsagging, three Strips of leather are sewed to its upper part at equal dis-tances from each other, and their other ends nailed to the rod, (SeeNo. 85.) The action of this sucker is something like moving a parasolup and down in water; the sides close as the rod descends and openwhen it rises. It is the simplest modification of the sucker known andprobably the most ancient. It is figured by Agricola, (vide C in No. 88) but
a This part of an atinospheric pump is sometimes named the sucker, the bücket, theupper box, the piston;—we shall generally use the first when speaking of the atmo-spheric pump ; and the last when referring to forcing pumps.