Page:Popular Science Monthly Volume 72.djvu/114

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PSM V72 D114 Artistically designed stone bridges without keystones.png
Typical Bridge of Substantial Character. Note the Absence of Prominent Keystones.

sometimes by a fourth. These watery mountains spread across the whole channel, and advance with a prodigious rapidity, rending and crushing everything in their way. Immense trees are sometimes uprooted by it and sometimes whole tracts of land are swept away.

Tidal Currents in Rivers[1]

There is no appreciable tidal effect in rivers due directly to the tidal attraction of the sun and moon, but the tidal wave in a river is

  1. See G. H. Darwin, "The Tides," etc., Scribners, 1898. This contains also an account of the Hangchow Bore based on Captain Moore's survey, to which we shall refer later on.