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drawn by six oxen; eight large cars, each drawnby four oxen; and the lighter materials in seven-teen cars drawn by two oxen each.

At a sufficient time previous to the removalof the materials for application, an intelligentofficer, Lieutenant Perry, was sent to superin-tend the cutting of channels in the masonry ofthe bridge, to receive the straining beams, R, towhich the tackles, G, ( 13 ), were to be fixed.

To facilitate the laying of the bridge, twostrong hawsers, (6), represented by the linesdrawn longitudinally under the floor of thebridge, fig. 6, were stretched across the gap asconductors, upon which the further end of thenet work might be hauled over.

A tarpaulin, (17), F F fig. 6, 4 feet wide, wasstretched along the outside ropes, as a blind forcattle and horses; and tackles H II , fixed to tw r oof the cross beams C C and to ring-bolts set inthe masonry below, to brace and steady thebridge. A railing, formed of posts and ropes,completed this extraordinary work; and thewhole was finished in time to open a passageacross the Tagus for the column of siege artil-lery, under Colonel Sir Alexander Dickson, whocrossed it on the 11th, and arrived at Sala-manca on the 20th of June.*

* A similar bridge was prepared at the New Museum, at