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have confirmed, rather than have questioned, theopinions of the engineer of that structure, whohas attained great eminence by many importantworks of acknowledged excellence.

It may be said that there is a professional im-propriety in referring to the Menai bridge, as isdone in these Tracts ; in answer, the author hasto observe, that Mr. Rennie was first employed( 1810 ) respecting the passage over the Menaistrait, and proposed to erect a cast-iron bridgeover it; but, in the year following, Mr. Telfordproposed to erect a bridge of the same kind forless than half the cost of the one proposed byMr. Rennie. Neither being adopted, the au-thor considered himself at liberty in the sameyear ( 1811 ) after Mr. Telford had proposed hiscast-iron bridge, to recommend a pendent bridgeat one-fourth of the amount of Mr. Telford’sestimate for a cast-iron bridge, which recom-mendation, “ membranis intus positis,” after alapse of nearly nine years, is assumed for Mr.Telford, and he is publicly thanked, in 1819 ,for contriving the plan at double the cost whichthe author recommended in 1811 .

By means of the geometrical methods of con-structing a catenary given in this work, andthe table of the dimensions of a catenary, theprinciples of pendent bridges here deduced havebeen rendered intelligible to very ordinary at-tainments, and of easy application.