( 3G9 )

sible, a secure communication, by repairing thegreat bridge: this brought again under consi-deration, the project which had been originallysuggested, and which, with some alteration, itwas now resolved to adopt. The propositionfor applying two stories or tiers of trestles hadbeen rejected, on account of the instability ofsuch a scaffolding; it was therefore determinedto construct trestles of dimensions sufficient tomake good, in one tier, a communication levelwith the road-way of the bridge. The trestleswere about twenty-six feet vertical height,formed of trees, in the rough, but strongly puttogether. The beams were likewise made oftrees recently cut, and unbarked; and planksfor flooring were found in the boat yards ofDresden .

The trestles were laid in the following man-ner, in succession. The first, being carried tothe brink of the broken arch, was thence lowereddown an inclined plane, formed by beamsplaced as in fig. 7, plate 9, and then hauled, bypeople on the other side of the gap, to the up-right position, preventer guys being used toe ase the operation : the legs of the trestles werepreviously cut to correspond with the inequali-ties in the bottom of the river, which were ac-curately determined by taking levels or sound-

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