Page:Popular Science Monthly Volume 72.djvu/112

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PSM V72 D112 Contrast in bridge construction 1.png

PSM V72 D112 Contrast in bridge construction 2.png

A Contrast in Construction.

decrease in width and depth of the Bristol Channel the tide enters the Severn with great force, forming a tidal wave or bore which at times attains a height of nine feet and has on several occasions caused great destruction, as in 1606, 1687, 1703 and 1883. The Bristol Channel also concentrates the great wave which gives Chepstow and Cardiff a tidal range which sometimes reaches fifty feet. In like manner, the tides which enter the Bay of Fundy between Novia Scotia and New Brunswick are more and more cooped up and rise higher as they ascend the strait, till they reach a height of seventy feet. But these changes are gradual, not really sudden enough to constitute a properly