7-ehnilding Lo)idon Bridge. SI 



at variance witli its bed and banks. Hence it is necessary to 

 ascertain the nature of the soil of the bed of tiie river and of its 

 banks at the several points of sinuation up us high as Tide- 

 end-town, wherever it may be hereafter, whenever there are 

 buildings to be sapped*; and this inquiry should be made in 

 the survey, which, by an extract from the Report of Mr. Telford 

 in the Phil. Mag. of May last, he has requested autliority to 

 get made, comj)laining that no such document exists; the per- 

 sons examined before him since 1800 up to this session of par- 

 liament, as to the effect likely to be produced by the enlarge- 

 ment of the water-way of London Bridge, having been able to 

 decide upon these matters without the data Mr. Telford now 

 thmks necessary. Such a river as the Thames, which, at a 

 mean width between London and Blackfriars Bridges, even 

 now the dam exists, having a velocity in the mid stream of 

 sixty-three ^ inches per second, or 3/^ miles per hour, at half 

 flood, requires some respect to be paid to its speed, its wind- 

 ings, and its fences, and will be found indignant to an altera- 

 tion of its ancient habits. The paradoxes which experiments 

 on the flowing of waters present, the recent history of the Eau 

 Brink as to its anticipated and its actual effect on the harbour 

 of Lynn, the erroneous calculations of the Royal Academy of 

 Paris in respect to the apparently simple question of the Paris 

 aqueduct, and those of Desaguliers and MacLaurin as to that 

 of Edinburgh, might cause some doubt of any opinion with 

 sufficient data, aiid much more of the determinations of mere 

 theory., from one of very advanced age, without any. The 

 question relating to the effects of the removal of the dam west- 

 ward, put in the Ibllowing manner, would cause more inquiry 

 than the present seems to have done. 



What effect would the introduction of another river on the 

 west side of London Bridge, of the same dimensions as the river 

 Thames at London Bridge, with a fall into it of two feet, have 

 upon the bed and banks westward at high water ? What effect 

 would the subtraction of a quantity of water, at low water, equal 

 to the surface of the river, six feet in depth at that subtraction, 

 have upon the river westward at that time of the tide ? It has 

 been maintamed, with reference to a compensation clause in 

 the bill for the new bridge, that, in cases of land-floods, the 

 removal of the dam of London Bridge would not cause an in- 



* See Appendix (A. 2.3, ZA Report. Lond. Port.) in which are given the 

 bornings from London to Blackfriars' Bridge, from which it ujipears tliat 

 the bed of the river in that part is gravel and sand, coarse and fine. 



f See .'{d Report, Appendix G. London Fort, and Plate i.'0, Appendix. 

 At Westminster, Mr. Labelye ascertained the velocity to be thirty-six inches 

 per second, 



creased 



