76

HISTORY OF ENGINEERING.

Book I.

The construction and demolition of their walls needed the aid of machinery, and amongthe Greeks a knowledge of all its proportions was thoroughly understood. The battering-ram, the balistre, the catapult®, the crane, the tortoise for filling up ditches and otherpurposes, and the several machines described for defence, show a thorough acquaintancewith the properties of the lever, the wheel and axle, the pulley, the inclined plane, the wedge,and the screw ; and Euclid’s Elements , collected about 280 years before Christ, for theinstruction of the pupils assembled at Alexandria, attest their advance in geometry.

Tlie walls which remain in part at Platea more distinctly show the arrangement of thetowers, battlements, and galleries be-tween them. In some of the towersare staircases, and the whole is con- ’structed of large stones.

The double walls of the Pelopon-nesus , also described by Thucy-:dides, were formed in portions of adouble circle, one towards Platea, •and the other towards Athens.

They were distant from each otherabout 16 feet, and the space so ob- 'tained xvas divided into rooms bycross walls, which tied and unitedthe whole together. At every tenthbattlement was a tower, extend-ing through both walls, and havingits passage through the middle overthe rooms, to which, during incle-ment weather, the guards might re-tire, and keep watch through theloop-holes contrived for the purpose.

(Lib. iii. cap. 21.)

Amidst the discoveries in Lycia ,made by Charles Felknves, Esq. a fewyears ago, and published by thatindefatigable traveller, were severalgates of peculiar construction. Thatat Penara is Cyclopean, and formed *of massive upright stones, withanother laid over as a lintel, nowbroken. (See Jiff. 85.) There is also one which forms the entrance to a tomb having apointed arch surmounted by the horns of a bull. (See Jig. 86.)

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Fig. 83.

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Fig. 84.

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Fig. 85.

Fig. 86.

There are great varieties of form given to the ancient portals, and it is curious to tracethe changes from the rude Cyclopean method of discharging a weight over an opening, bythe gradual projection of the stones meeting in the middle, to the formation of an equilateraltriangle, as used by the Egyptians at a very early time, two stones, like the chord of twoarcs, being placed one against the other. The approach to the regular portal is made at thegate of Penara, and this is rendered beautiful by the improvements added in that at Sidyma,