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HISTORY OF ENGINEERING.

Book I.

has a fertile soil, produces fine fruits and wines, and has an atmosphere of great serenity,no day ever passing without sunshine. This island was occupied by a colony of Greeks,some from Crete , and some from Thessaly, at a very early period; and Homer tells us thatTlepolemus, son of Hercules, took with him a colony from Argos to Rhodes , and after-wards joined the expedition against Troy : at that time the wealth and power of its in-habitants were considerable, lie divided the island into three independent states, Lindus,Cainirus, and Ialysus : the first of these, which gave birth to Chares, the architect of thecelebrated Colossus, stood on the east coast of the island; Camirus , on the western coast,and Ialysus on the north side. Some time afterwards, during the Peloponnesian war, thesethree states were united, and the city of Rhodes , built in a very advantageous situation,became the common capital of the island, flourishing in commerce, arts, and arms, andextending its dominion over a large portion of the contiguous continent. It was situatedon the east coast, at the foot of a gently rising hill, in the midst of a plain, abounding withsprings and fruit trees. Strabo informs us that in ancient times few places were preferableto it.

Hippodamus , a native of Miletus , who had gained great reputation by his works at thePiraslis, already alluded to, arranged the plan of the new city, and superintended theerection of the walls, gates, and public buildings. According to Strabo , its form was thatof a vast amphitheatre, surrounded with walls, like those of Munychia, embellished withstraight and wide streets, large squares, and numerous splendid edifices, among which was theIlaleum, or temple to Apollo.

The haven or harbour was of considerable extent, and the entrance to it was by a passagebetween two rocks, 50 feet apart.

The Rhodians , for centuries, were famous for the study of the sciences, and by many,Rhodes was reckoned equal to Athens for the number of its learned men ; the in-habitants were in amity with all nations, and their merchants, from the trade they carriedon with Egypt , became so enriched, that the whole city was supported by them. It wason the occasion of Antigonus not being able to separate them from the cause of Ptolemy ,that he sent his son Demetrius Poliorcetes , or city taker, with ships to intercept the tradebetween the ports of Rhodes and Egypt . The Rhodians , however, were successful in allthe combats; at which Antigonus became so incensed, that he furnished Demetrius withadditional ships, and all manner of engines to besiege their city. The fleet consisted of 200men of war, and 170 vessels, which carried 40,000 soldiers, besides horse and auxiliaries.A thousand other vessels, belonging to merchants, followed in the train.

Demetrius drew up his fleet, which contained engines of every kind, capable of producingdestruction, in the following manner : —those which discharged darts or arrows, three spanslong, in front; the vessels which contained the cavalry in the second rank, and in the rear thetransports, which contained corn and provisions; the whole sea being, as it were, coveredwith vessels. On his arrival, he landed all his men, and took his station within the cast of adart from the walls of the city, throwing up an earth wall, fortified by large trees, as a pro-tection against any sally from the Rhodians ; he then commenced dredging the port, andrendered it sufficiently deep and spacious to hold his fleet. His next operation wasto construct two engines called testudoes, which he placed upon the decks of twotransports, one of which was to guard against the stones thrown by the enemy, and theother the darts and arrows discharged by the machines on the walls.

Plutarch informs us that Demetrius had a thorough knowledge of mechanics, and that inevery thing he did, there appeared a grandeur of design, and so much invention, that hisenemies, pleased with the beauty of his contrivances, stood looking with admiration athis galleys of fifteen or sixteen banks of oars, and his engines, which were called helepoles,in consequence of their employment in taking a city. The largest had a square base, eachside of which measured 48 cubits, and its height was 66 cubits, but it diminished on allsides towards the top, and therefore resembled the frustum of a pyramid. It consisted offour stories, each having an opening for the discharge of missiles. Vitruvius informs usthat these engines were made by Epimachus, an Athenian, whom Demetrius Poliorcetes had in his train, and that it was secured by hair cloths and raw hides, so that it mightwithstand the shock of a stone 360 pounds weight, thrown from a ballista. The entiremachine, it is said, weighed 360,000 pounds.

At this time, Diognetus the architect was paid an annual salary for his skill in main-taining the walls and places of defence ; but during the siege, Callias, an architect ofAradus, arrived and exhibited a model of a wall with a revolving crane, by means of whichhe could suspend an helepolis near the spot, and swing it within the walls. V hen theRhodians saw this, they dismissed Diognetus , and appointed Callias to fill his situation,and to prepare his machine against the helepolis, and swing it within the wall, as he hadpromised ; when he was obliged to confess his inability. Diognetus was then entreated toaid his countrymen, and he consented, upon the condition of having the machine if he suc-ceeded in removing it: this being agreed to, he ordered a hole to be made in that part of