h perfect | rises a little, and then, after it has passed, the bridge As canals can be crossed only on bridges, large | success. returns toits proper position by the action of gravita- numbers of these structures are required for the| The bridge as represented in the engraving is bal-| tion. The… … too complicated, or were boat has passed, to its pro- otherwise objectionable. zontally upon a pivot, its support consisting of cir- | per position in line with the road. The ring, 5, rests The bridge here illustrated is exceedingly simple| cular tracks running on rollers so arranged that | in like…
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