the Intended Thames Archways, &c. 49 



uppermost of those strata. The dislocations above men? 

 tioned present to naturalists a most favourable opportunity, 

 bv ascending from the several chalk-pit3 in Greenwich, 

 Chalton, Woolwich, £cc. towards the top of Shooter's Hill, 

 of distinctly tracing, as I apprehend, every stratum in the 

 London clay. I have ventured to suggest these, as among 

 the numerous methods which might be taken to ascertain, 

 whether regular strata have already or may hereafter be 

 reached by the borings or sinkings for the Rotherhithe arch- 

 way : justice, perhaps, requires of me to say, in this place, that 

 the borings above given, and specimens shown to me by Mr. 

 Vazie, present to me none of the characters of the undisturbed 

 London strata, but decidedly those of alluvial matters ; and 

 which matters, I have too much reason to fear, extend 

 lo still vastly greater depths at Rotherhithe. I have hinted 

 elsewhere, that had the regular or clay-ball stratum appeared 

 at the surface on each bank of the river, still, before an ex- 

 pensive tunneling is undertaken, it would be prudent to bore 

 at short intervals across the river sufficiently far into the clay 

 to ascertain whether any fissures filled with alluvial matters 

 exist therein under the river, which it may be extremely dif- 

 ficult if not impossible to work through. It has long ap- 

 peared probable to me, that the vale of the Thames, from 

 Charing-Cross to the Tower on the north side, and from 

 the foot of Camberwell Hill to the foot of Plough-Garlick 

 Hill on the south, has been occasioned by two fissures, one 

 along each of those lines or nearly, and that the whole of 

 the strata between those lines are sunk down, perhaps, to a 

 depth far below practicable boring or well-sinking, and that 

 this chasm (a similar and remarkable instance of which I 

 have traced at Woburn, in Bedfordshire,) has been filled up, 

 almost to its present level, by successive alluvial deposits of 

 sand, clay, and other matters washed from the neighbouring 

 eminences; and that, in after and more quiet periods, the 

 growth of peat, and the gradual subsidence of mud, have 

 completed the filling up of the valley to its present state. 

 Having far exceeded the limits which I proposed to myself 

 when I began this letter, I beg to conclude, and am, 



Yours &c. 

 12, Upper Crown-street, Weitminster, > T _, 



Ztat May, 1806. JOHN FAREY. 



Vol. 2S. No. 97. June 1806. D VIII. Me- 



