rebuilding Londuii Bridge. 29 



wlictlier a more t'requent inundation and saturation with water 

 of" the low lands will cause miasms and pestilential diseases 

 again to prevail, should the means of stopping such inundations 

 or of quickly draining off the water not be immediately ob- 

 tained. They look forward with great anxiety to the experi- 

 ment; and the knowledge that this dam has existed many 

 centuries, that the river passes through a dense population, 

 that the estates of individuals have been regulated by it, that 

 the levels of the lowest floors of houses and those of the streets 

 in the low lands adjacent, have reference to this habit of the 

 I'iver, adds much to the excitement; for the intenseness of the 

 interest always increases with the hazard of the throw. The 

 complaints of the inhabitants on the banlis of the river, like 

 those of the dumb creature subject to the knife of the surgeon, 

 are not lieard in the eager pursuit of knowledge, and in the 

 speculation of future amelioration. There are others who have 

 great influence, and are urgent for the demolition of London 

 Bridge, looking to their own gain* in the erection of a new one. 

 A mathematician, like to him of Laputa, has brought his im- 

 plements to the question, and, without sections, without levels, 

 and ignorant of the soil over which the river flows, or against 

 which it impinges at its sinuosities, knowing neither what may 

 be overflowed, nor what may be sapped, has, by a kind of in- 

 tuitive philosophical tact, determined that, after the removal 

 of the dam, the stream will flow on as harmless and obedient 

 as heretofore f. Presuming there may be some of your readers 

 unable to discover trudi except by induction, and others cos- 

 tive of their belief in the delirations even of a great teacher, 

 and thinking that they may be desirous of viewing this im- 

 jiortant question by any glass, however weak its power, your 

 correspondent ventures to oflfer that by which he views the 

 question, and solicits the shelter of a few pages for the follow- 

 ing observations in your journal. 



The writers on the ordinances of rivers consider the courses 

 and velocities of diem dependent on the nature of the ground 

 over which they pass, as well as upon the heights from which 

 their waters descend. For example: water descending from a 

 hei'rht on rocky ground, which it cannot remove, rises, spreads, 

 and forms a lake; and proceeds with diminished vekjcity to 

 the lowest point, and there cascades ; advancing at the rate of 

 forty-five inches per second, it will drive flint stones about the 

 size of an egg before it, and rise and spread until its velocity 



• There is no tloiibt tliat that writer here ascribes the efforts which 

 have been made with so niucii success to procure the cleiiiolition of Lomloii 

 Bridge to their real cause; ahhou!.'li the influence of a Coinmirtee of the 

 House ofConinions was cnipIo3cd for the attainment of the object. —linrr. 



t 'See Dr. Iluttoii's Anssvcrs, Api.. 1th Import, 18'.'!. 



is 



