512 MESSES. WHITAKEB AND JUKES-BBOWNE ON [Aug. 1 894, 



The only standard of level that naturally occurs to us is the 

 Ordnance datum, or mean sea-level, as that is the only one easily 

 and universally available. In the following remarks, therefore, we 

 shall refer to depth below Ordnance datum. In the case of Culford 

 and Ware, however, the reference of the figures to this datum makes 

 no difference, the two sites being at about the same level. 



In this matter it is noteworthy that heretofore the oldest rocks 

 yet reached by deep borings in South-eastern England are those 

 that come to the highest level ; Silurian beds having been reached at 

 Ware, Devonian at Cheshunt and London (Meux's), Red Rocks of 

 doubtful age, but now generally thought to be Old Red, at Streatham 

 (where something suggested that the passage-beds from Silurian 

 to Old Red had been touched), Crossness, Kentish Town, and 

 Richmond, this last being the deepest, and Carboniferous beds at 

 Harwich and Dover, as well as at Burford, in the Jurassic tract of 

 Oxfordshire. 



Again, Ware is the most northerly of the deep borings in and 

 near London, where they most do congregate, and it shows not only 

 a slight northerly rise of the floor of older rocks, but also a rise 

 in the divisions of those rocks, resulting in Silurian beds coming 

 next beneath the Gault. 



These two points tend, therefore, to give some slight support to the 

 view that the old rock at Culford may be pre-Carboniferous, and 

 perhaps pre-Silurian, in age. Not that this support is worth much, 

 but, having so little whereon to float conclusions, even a straw must 

 be taken into account. 



On the other hand, however, the fact that at Harwich, which is 

 nearer to Culford than any other of these deep borings, it is Car- 

 boniferous slate that has been found, and that this is, in some 

 respects, not unlike the harder parts of the Culford rock, naturally 

 leads the sanguine to hope, if not to expect, that the latter too may 

 be of Carboniferous age. Should this view be right, the likelihood 

 of still higher Carboniferous and coal-bearing rocks occurring 

 underground somewhere in the Eastern Counties is of course 

 greatly increased. 



The nearness of older rocks to the surface at Culford was un- 

 expected by us ; perhaps, indeed, no geologist would have ventured 

 to predict that such rocks would have been reached there, except by 

 a boring of much greater depth. One might fairly have expected 

 to go at least 1000 feet, and to have found the Lower Greensand 

 and the Jurassic Series well represented, more especially perhaps 

 the latter, seeing that the outcrop in the neighbourhood of Ely is 

 within 20 miles of Culford. 



The accompanying table shows the relations of the various borings 

 that reach the older rocks in the London Basin, including therein 

 the Chalk tract as well as that of the Tertiary beds. The point 

 clearly brought out by it is the sinking of the floor of older rocks 

 southward, in the district over which the borings occur, the only 

 exceptions being Harwich, which should come second in the list, and 





