128

HISTORY OF MARINE ARCHITECTURE.

Diognetus, to whom the republic gave a yearly and respectable pension onaccount of his abilities; and that another engineer, named Callias, camefrom Arado to Rhodes, and desiring to be heard by the people, exhibited ona part of their ramparts a machine, which was the ship-lifter in question.It turned easily, and taking up an heliopolis, which had been purposely broughtnear the wall, threw it within the bulwarks. The Rhodians, who beheld withadmiration the surprising powers of this engine, took from Diognetus thepension which they had hitherto given him, and bestowed it upon Callias.Callias, however, did not long enjoy their bounty ; for when Demetrius be-sieged the place, and employed his dreadful heliopolis, he confessed the impo-tence of his own contrivance when opposed to a tower of such enormous weight.He constructed, however, it may be presumed, corvi capable of lifting an helio-polis, or moving tower of the second order ; and if these towers are supposedto have been lighter than the gallies which Archimedes is said to have grappledand raised so easily, it will follow, that, at least, the machine of Callias differedfrom that of the Syracusan in this only, that the latter was capable of raisinggreater weights.

Plutarch gives the following description of this wonderful corvus : “ On thewalls,” says he, “ were vast machines, which advanced and suddenly droppedover the gallies large beams, to which were fastened irons, armed with hooks,which having grappled them, and lifted them by means of counter weights,suddenly let go their hold, and thus caused them to sink from the force of theirown fall. By another operation, after they had lifted them by the prow withgrappling irons, and raised them nearly upright out of the water, they plungedthem into the sea, or drew them toward the land with ropes and hooks ;sometimes, after whirling them in the air, they struck and shattered themagainst the points of the rocks which projected at the feet of the walls.Gallies thus incessantly taken up, and suspended above, must have presentedthe most frightful spectacle; for after the men who were in them werescattered by the violence of the motion, and cast to a considerable distance aswith a sling, the vessels were shattered against the walls, or, the engines lettingthem loose, they fell and sunk into the sea.

“ With respect to the corvus, or u^ayr,, described by Polybius, which has aclaim to previous notice, but which, for several reasons, is here mentionedlast, it is said, that the ships of Marcellus having advanced close to the wallsof the city, Archimedes caused a claw of iron, fastened to a chain, to be let

fall