Annual report upon explorations and surveys in the department of the Missouri . utof the canon makes its upper width from 2 to 3 miles. Here occasionally natureinterposed great obstacles to a passage. In a nanxrw bed the riAer ran by AAith thevelocity of a mountain stream, without foothold between it and the Avails beside it,their inclination so near a vertical as to render the cost of blasting for a roadway aquestionable expense. Numerous bridging was to be aA^oided on account of the situa-tion and the spring rise of the riAer. At such places the river was occupied for apassage-way, and these
Annual report upon explorations and surveys in the department of the Missouri . utof the canon makes its upper width from 2 to 3 miles. Here occasionally natureinterposed great obstacles to a passage. In a nanxrw bed the riAer ran by AAith thevelocity of a mountain stream, without foothold between it and the Avails beside it,their inclination so near a vertical as to render the cost of blasting for a roadway aquestionable expense. Numerous bridging was to be aA^oided on account of the situa-tion and the spring rise of the riAer. At such places the river was occupied for apassage-way, and these were by far the most expensive points. As the riAer descendsthere is found a greater Avidth of room, a small bench generally betAveen the waterand the mountain through which Avas easily effected a clearing giving a passage-way. At some points Avhere existed no bench or place for a roadway by the riAer bank, themountain and slope being of rock and very steep, a high sustaining wall was neces-sary, in some cases as great as 20 to 30 feet (Fig 1). At other points, the mountain. Fie. I.
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Keywords: ., bookcentury1800, bookdecade1870, books, booksubjectnaturalhistory
