178 



RENNIE'S BRIDGES. 



PART VII. 



The project of erecting a new bridge to connect the 

 Strand, near Somerset House, with the Surrey side of the 

 Thames at Lambeth, was started by a Bridge Company 

 in 1809 a year distinguished for the prevalence of one 

 of those joint-stock fevers which periodically seize the 

 moneyed classes of this country. The first plan consi- 

 dered was the production of Mr. George Dodds, a well- 

 known engineer of the time. The managing committee 

 were not satisfied with the design, and referred it to 

 Mr. Rennie and Mr. Jessop for their opinion. It w;is 

 found to be for the most part a copy of M. Peyronnet's 

 celebrated bridge of Neuilly, with modifications rendered 

 necessary by the difference of situation and the greater 

 width of the river to be spanned. It showed a bridge 

 of nine arches of 130 feet span; each being a com- 

 pound curve, the interior an ellipsis, and the face or 

 exterior a segment of a circle, as in the bridge at 

 Neuilly. 1 The reporting engineers pointed out various 



1 In their report on this design, Mr. 

 Kennie and his colleague observed: 

 " We should not have thought it ne- 

 cessary to quote the production of a 

 foreign country for the sake of show- 

 ing the practicability of constructing 

 arches of 130 feet span, had we not 

 been led to it by the exact similarity 

 of the designs, and by the principle 

 which is therein adopted of the com- 

 pound curve ; because our own coun- 

 try affords examples of greater bold- 

 ness in the construction of arches 

 than that of Neuilly. There is a 

 bridge over the river Taff, in the 

 county of Glamorgan, of upwards of 

 135 feet span, with a rise not exceed- 

 ing 32 feet, and what is more re- 

 markable is, that the depth of the 

 arch-stones is only 30 inches ; so that 

 in fact that bridge far exceeds in 

 boldness of design that of Neuilly." 

 [See our Memoir of William Edwards 

 in Vol. I. of this work.] After some 

 observations as to the importance and 

 necessity of making a bridge in such 

 a situation, at the bend of the river, 

 with as large arches as possible, to 



accommodate the navigation and pre- 

 sent as little obstruction as possible to 

 the rise and fall of the water, they 

 proceed : " We confess we do not 

 wholly approve of M. Peyromu't's 

 construction as adapted for the in- 

 tended situation. It is complicated 

 in its form, and, we think, wanting 

 in effect. The equilibrium of the 

 arches has not been sufficiently at- 

 tended to ; for when the centres of 

 the bridge at Neuilly were struck, 

 the top of the arches sank to a degree 

 far beyond anything that has come to 

 our knowledge, whilst the haunches 

 retired or rose up, so that the bridge 

 as it now stands is very different in 

 form from what it was originally de- 

 signed. No such change of shape 

 took place in the bridge over the 

 Taff (Pont-y-Prydd) ; the sinking after 

 the centres were struck did not amount 

 to one-half of that at Neuilly, although 

 the one was designed and built under 

 the direction of the first engineer of 

 France, without regard to expense, 

 whilst the other was designed and 

 built by a country mason with par- 



