The Viaduct Works' Handbook

39 IRON PIERS, ABUTMENTS, AND FOUNDATIONS OF BRIDGES. The employment of iron in the construction of piers, abutments, and foundations of bridges, presents so many advantages over wood stone or bricks, even where these materials can be obtained of goo quality at moderate prices, as to have led to its almost general use. It is especially adapted to the piers of bridges manufactured in this country and exported to a colony; and, apart from its economy, and durability, it is easy of transport, and offers advantages over other materials in respect of the rapidity with which it can be erected, all the parts being fitted together in this country, it requires com- paratively little skilled labour abroad. Cast-iron is chiefly employed, and in the form of hollow oylin- drical piles, varying from 1 foot diameter up to about 10 feet diameter, and where light loads are to be carried sometimes solid wrought-iron piles, from 4 inches up to 8 inches diameter, with enlarged cast-iron screws attached to the lower end, and screwed into the ground, have been employed with advantage. . The form and dimensions of the piles of any pier must at all times very much depend upon local circumstances, and the nature of the ground, the height they are required above ground, the depth of water, if any where they are required, &c. It will, therefore, be advantageous at all times in sending any requisition from abroad for materials for iron bridge piers to be made in this country, to accompany sued with as much information as to the nature of the ground, and, ifpossible, in the ease of a work of considerable magnitude, borings of the site of intended piers, as the want of such information has occasionally led to sending from this country material for foundations altoget er unsuitable for the intended purpose. It may be sufficient here to Xthat piles from 12 inches diameter up to 30 inches diameter are usually made to screw into the ground, unless this is imprae ticable in consequence of the hard nature of the ground, which, it hannens to be rock, the bottom of the pile may be cast with a base Plate as in the case of Crumlin Viaduct, and bolted directly nonit - and if compact gravel, it is generally sufficient to bed the upon 16, ac0 1 o