INTRODUCTION.

5

House of Commons *, the author, judgingfrom authority, is fearful that what he hasassumed, or what he has deduced, is nottrue.

The exposition of the properties of thecatenary, from which alone the true princi-ples of constructing bridges by suspensioncan be derived, and the application of thoseproperties to such a practical case as thatof the Menai bridge may afford to architects,who may be employed in the erection ofsuch works, the means of determining, in assimple a mode as possible, the relativeproportions of the parts of them. j~ The

* The evidence of Mr. Rennie before the Committeeis of a general nature. He says, “ I have no doubt ofthe practicability of constructing such a bridge; and Ipresume that Mr. Telford has taken care to have all theparts sufficiently strong, and so well connected together,as to be able to sustain the weight he has calculated itto bear; but I have not made any calculations of theactual strength of the bridge which Mr. Telford pro-poses.”

f In the last number (20) of “ The Journal ofScience, &c.” edited at the Royal Institution, is a letterfrom Mr. Davies Gilbert , “ On some properties of theCatenarian Curve, with references to bridges by sus-pension.

B 3