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HISTORY OI’ ENGINEERING.

Book I.

a part of Aurelian 's wall, having open arches at the top, which served as an aqueduct;this portion is of greater antiquity, probably of the time of Claudius.

In the time of Pope Eeo IV. the Vatican was walled in, and six gates admitted to itsenclosure. In the year 1143, Urban VIII . built another wall on the outside of theEeonine city.

Circeiton, or Circeia ( Jig . 103.), not far from Anxur, is situated on the low land bor-dering on the sea. The promontory upon which it stands, in the days of the Argonauts , issaid to have been occupied by the Turrheni. lire Volscians are reported to have takenpossession of it, in whose hands it remained until Tarquinius Superbus conquered it,when he sent his son with a Turrhenian colony to settle there. The Volsci again recoveredit, and drove out the Romans, in the time of Coriolanus, and it afterwards became a Romanmunicipium.

Fig. 103.

CIRCEIUM.

An area of about 600 feet by 300 is enclosed by a wall of polygonal blocks, laid afterthe manner of the cyclopean, and the single gate which enters it at the north-east angle iscurious for the size and disposition of the stones which discharge the weight over theopening, one of which, nearly 8 feet in length, lies like a lintel in a horizontal positionupon two others which project over the perpendicular line of the jamb, to relieve itsbearing. (See Jig . 104.)

Fig.104.

Spello in Umbria affords us an excellent example of a gate flanked by polygonal towers:there are three entrances decorated with simple pilasters, and a gallery above. The stair-cases within the towers are circular, and the tops have the first indications of machico-lations. The battlements remain, crowning portions of the walls which once surroundedthis ancient city, and in them we recognise the Greek or Etruscan origin, which was notdeparted from during the middle ages. (See Jig. 105.)