15

the ratio of 3.52 to 1; more than is performed atWaterloo bridge, though of granite, in the ratio of2.22 to 1 : and Ammanati performed more with mar-ble than is performed at Waterloo bridge, withgranite, as 22.2 to 8.0; more than is performed atthe Southwark bridge with iron as 96 to 80; andthan at Craigellachie in Morayshire, as 99 to 80. *

It is not probable that Edwards, at Pont y ty Prydd,learned his knowledge from Ammanati , but it is pro-bable that Perronet derived some information fromthe work of Edwards. Taking into account thedates, Wales ranks before France in the art of bridgebuilding, in respect to the due adjustment of strengthto stress; and in respect to the theory and practice ofbridge building generally, the most eminent mathe-maticians, engineers, and architects are less advancedthan the Italians were two centuries ago, viz. in thetime of Galileo and Ammanati .

In the Report of tine Menai Bridge, ordered to beprinted February 18th, 1819, Mr. Telford observes,in his Report, “ It is only a few years ago thatbridges of cast-iron, of one hundred feet span, wereventured upon with timidity; and now, although

author believes that economy is the result of knowledge, and extra-,vagance of the want of it. The architect of Santa Trinita recom-mended what he thought proper; and so doubtless did he of Alcan-tara, and therefore Ammanati may be accused, with as much pro-priety, of recommending needless solidity for selfish purposes, as,the architect of the bridge of Alcantara. No engineer, called uponto act from his own knowledge, can be justified in putting to,hazard his own character, by making a building less strong thanhe thinks it ought to be, unless his employers undertake the in-surance of that character, as well as of the work at the same timeendangered, or considered to be so.

* See the Tables of Bri dges.