the intended Thames Archways, &c. 47 



On the Suuth Side. On the North Side, 



teet. Feet. 



55 (Brought over) 45 



8 Chalk. 7 Light blue and brown 



stratum resembling sand. 

 4 Concreted rock. 3 Sand* 



16 Green dry sand. 4 Variegated blueandbrown 



hard clay. 

 3 In firm gray wet sand. 2 In wet sand. 



86 61 



The river in this place being 7724 feet wide at high water of 

 spring tides, and then 38 feet 10 inches deep in the middle. 



I have already, sir, declared myself convinced * of the 

 practicability and usefulness of forming archways under 

 Rivers in almost any situations, and it is principally from 

 a desire to contribute mv mite towards promoting this 

 highly useful mode of communication that I have troubled 

 you herewith. The shaft or well at present sinking in 

 Rotherhithe, is, as Mr. Vazie informs me, intended, in 

 the first instance, for ascertaining, more fully than boring 

 can do, the nature and condition (as to springs of water) 

 of the strata or alluvial matters under the south bank 

 of the riveT; and, during the progress thereof, I beg to 

 call the attention of Mr. Vazie and those concerned, to 

 the. circumstance of preserving frequent and ample speci- 

 mens of all the matters sunk through, with reference to the 

 exact depth and thickness of each, and the state of the wa- 

 ter, as ascertained by the strokes of the engine-pump from 

 time to time. I beg further to mention, that, as far as my 

 recollection of Mr. Smith's map now serves me, the top of 

 the great Chalk stratum above mentioned, is to be found on 

 ihe surface at no great distance south of the head of tbe 

 Croydon canal, about ten miles from London : also, that at 

 the foot of Ridge Hill, \G\ miles from London, on the road 

 to St. Albans, the same stratum appears again; the surface 

 between these two places (passing through the metropolis) 

 being occupied by the whole or the lowermost of the strata 



* Dr $■■<■.'-. OyclKpwdia, article C'n/?"/, ioct. Thanm Rlvfe*, Sic. 



foiiipnlii'iulcd 

 I 



