and of the intended Bridgt, 6j 



quire to be of the large dimenfions which may at firft be 

 imagined : the truth of the principles was fully proved by the 

 very ingenious, though apparently flight, fcaftblding, over 

 which the arch of Wearmoulh was turned ; and they may 

 be ill nitrated by ftatjng, that the greateft ftone arches are 

 turned upon centres formed of timber. When the courfes of 

 ftone have been brought up to near the crown of the arch, 

 on each fide, the whole refVs upon the timber centres, and 

 in large arches this weight is very great : the centre muft, 

 however, be equal to fupport the weight; otherwise it would 

 give wav, and the done-work would Fall down. 



The iron arch is, in fact, no more than a framing fimilar 

 to that for the centring for a ftone arch, with this difference, 

 that the iron framing has little more to carry than its own 

 weight. The iron work having much more ftrength than 

 timber, may be made proportionally fmaller. In making 

 and putting up timber centres, there muft be props and fup- 

 ports, and the fcaffolding for fupporting the iron framing 

 may be compared to thefe props and fupports. 



By deepening and embanking the river, much ufeful fpace 

 will be gained, and the properties along each bank of the 

 river, as well as the ftreets adjoining, and leading from thence 

 into the city, will, bv a judicious arrangement, be rendered 

 very valuable. Depofits, and public markets for coals, may 

 ajfo be formed under the wharfs, by which means the light- 

 erage of coals brought from the pool up as far as Blackfriars 

 bridge would be completely faved. This plan is propofed by 

 Mr. Douglafs, who has given a full defcription of it in the 

 Appendix to the third Report of the Select Committee of the 

 Iloufe of Commons. From his eftimatcs on the general con- 

 fumption of coal in London, it appears, that the favings in 

 two years will be adequate to the expenfe of creeling the new 

 iron bridge. This plan merits mature confideration. The 

 coals being regularly fupplied, would tend to prevent hidden 

 injurious competition, which of late years has been fuch a 

 burthen on the public. 



If this part of the. plan for improving the port of London 

 be fuccefsfully executed, we fhall no longer be reproached by 

 foreigners, that we have one of the fined rivers in the world 

 running through our principal city, yet that we lufler its 

 ufefulnefs to be in a great meafure dedroyed by maintaining 

 a ftone embankment acrofs the molt valuable part of it, by 

 fuftering its fhores to exhibit an extent of mud, indead of con- 

 verting them into ufeful wharfs; and its banks to be covered 

 with mean and fhapelefs buildings, indead of edifices luited 

 to fo noble a fituation, and worthy the commercial metro- 

 polis of Europe. 



E 2 X. On 



