INTRODUCTION.

By the second report, “ Holyhead’s Roadsand Harbour, 9th June 1810, ordered to beprinted by the House of Commons, ” a cast-iron bridge was proposed by Mr. Rennie tobe constructed over the Strait of Menai atYnys y moch, estimated at 268,500/. ; andby another report of May 30. 1811, acast-iron bridge was proposed to be erectedat the same place by Mr. Telford, esti-mated at 127,331/. These reports havingfallen into the hands of the writer of thistract, he was led to an inquiry into theproperties of bridges by suspension, andproposed by letters June 28. 1811, andsubsequently, to those to whom the in-vestigation of the subject of the Menaibridge had been principally entrusted, the

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