The theory, practice, and architecture of bridges of stone, iron, timber, and wire by John Weale

Author:John Weale
Language: eng
Format: epub
Publisher: J.Weale

1 A long pointed iron rod may be used with advantage in the general examination of the ground, and of the bed of a river. The comparative ease or difficulty with which any rod may be forced down into a sound bed of clay that may be at hand, and into the bed of a river, or into the ground on its banks, will enable an observer to judge with tolerable accuracy of the soundness or unsoundness of the latter before the process of boring is undertaken.

be traced upwards; and in old countries, ruins of earlier works or existing structures on or near the banks will be often found to retain evidence of inundations by stains, or by the adhesion or deposit of weeds and other drift, in such manner as to be easily recognised by the observant. In new countries, trees and underwood, or brush, near flooding rivers, retain certain indications of the. heights to which floods rise by the drift which hangs on their branches, and by the discoloration which intercepted scum and earthy matter that may have been held in suspension in the flood-waters occasion.

The object sought in the erection of a bridge is an uninterrupted road or way over or across a river or other obstruction in the most convenient manner and place for the traffic or uses of the road or way, and this must be kept steadily in view, though in seeking to attain it no other interest should be sacrificed, and nothing done to bar future improvement, nor should the removal of one obstruction be made productive of another. A river may not be liable to high floods, and it may be a matter of calculation that the piers or other substructions of a bridge built in a certain manner and of a certain extent will not hold the water up sufficiently to endanger them, but the water may nevertheless be dammed up in such manner as to interfere with the proper drainage of the land, even if low lands are not directly flooded by the waters of the river breaking in upon them. Again, a river may not be itself navigable, but it may be susceptible of being made so, or of being connected with an artificial navigable water-way; and care should be taken, therefore, in aiming at the primary object of a bridge, not to erect what may be a bar to the establishment of an efficient way for commerce in another direction.

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