Author Description

This historic book may have numerous typos and missing text. Purchasers can download a free scanned copy of the original book (without typos) from the publisher. Not indexed. Not illustrated. 1843 edition. Excerpt:...or their hold, to prevent the generation of such action. Indeed it does not appear but that a system of vertical timber bracing between the sills and curbs of the roadway and the main chains, commencing by an abuttal on the podium of the piers or suspension towers, may be introduced in connexion with transverse bracing from main chain to main chain in the deep parts, or where the head-way would not be affected by it, with economy and advantage. Such a system as that here suggested would adapt itself readily and without derangement to the expansion and contraction of the chains and rods, and tend materially to stiffen the road-way, whilst it would check any approach to the undulations, which, without a system of vertical bracing, are found to follow the vibration of the road-way in tempests. Vertical bracing under the road-way occupies head-way below, or renders it necessary to raise the bridge so much higher to preserve it, without assisting in any degree to steady the chains and give them the aid of the road-way in resisting impulses to motion. For the reason last stated in objection to vertical bracing under the road-way of a chain suspension bridge, the plan proposed by Mr. Stevenson of Edinburgh (see Plates 104, 105, 106, and 107), of laying the chain under the road-way, is objectionable; but in cases where no inconvenience would result from this, it is a plan that has nothing to recommend it before the erected rib suspension system, but, on the contrary, the mode of construction it involves is less sound, the result is far less sightly, and certainly the plan presents no advantage, as far as economy is concerned, over that other and more eligible mode of construction which is here contrasted with it. Both plans or modes of construction are...