The sides were of smooth stones about four feet high, and the roof was made by stones lapping over like the corridors of the buildings. At a short distance from tha entrance, the passage turned to the left, and at a distance of 160 feet it was completely blocked up by the ruins of the roof which had fallen in. What was its direction beyond, it was impossible to determine, but it certainly did not pass under the palace, as has been supposed."

A fine modern aqueduct was built at Rio Janeiro, in 1740, in imitation of that of Lisbon, and in some of its proportions, is hardly less imposing. " It " of two walls about six consists," says McLuccock, feet, arched over, with suf-

* P. 78, Book iii., of De Soils' History of Mexico done into English by Thomas Townsend, London, 1779,

t Clavigero in Cullen's translation, vol. ii. p. 204., London Edition in 4to. 1787, p. 204, t Book iii., Class x., p. 55, Townsend's translation. 5 Stephens' vol. p. 321., at -

ii, Palenque. %

76 PRELIMINARY ESSAY.

ficient space for workmen to enter it occasionally and pass through its whole length. At suitable intervals, there are openings for the admission of light and air. Within it, is laid the canal, about eighteen inches wide, twenty-four deep, and three miles long. It

commences at the bottom of the lofty conical peak of the Corcovado, where the waters flowing from that mountain, are collected into a covered reservoir, and thence conveyed into the canal. Their course from the summit is through deep and shady woods, and the canal is defended from the sunbeams, and thus, until they reach the city, little of their * freshness is lost."