754. PROF. J. W. JUDD ON THE NATURE AND RELATIONS OF - 
Whether we accept the lacustrine theory of the origin of the Old 
Red Sandstone or not, I think there will be equal difficulty in ex- 
plaining the presence in close proximity of such remarkably different 
representatives of the Devonian period as the highly fossiliferous 
Hifelian type and the barren Old-Red-Sandstone type. 
Every argument in favour of the Poikilitic age of the Kentish Town 
and Crossness beds applies a fortiori to those at Richmond, which 
certainly present all the peculiar characteristics of the typical Triassic 
strata in a marked degree, as I have already pointed out. With 
the new light thrown on the question by the borings at Gayton and 
Northampton, I cannot avoid the conclusion also that the strata 
found at Kentish Town and Crossness are more probably of post- 
Carboniferous than of pre-Carboniferous age. It may, indeed, be 
argued that as in the Ardennes we have the lowest member of the 
Devonian (the Gédinnien of Belgian geologists) underlying strata of 
the Hifelian type, the same may be the case under the London 
Basin. But against this view must be set the fact that MM. Gosselet, 
Six, and Barrois, who have such an exact knowledge of these Gédin- 
nien strata of the Ardennes, fail altogether to recognize any resem- 
blance between the Richmond rocks and those strata, but on the 
contrary believe the latter to be Trias. 
To sum up the evidence on the age of these variegated rocks at 
Richmond, Kentish Town, and Crossness, we may admit that the 
resemblances to the Old Red and the New Red rocks are about equal : 
but considering the undoubted presence of Devonian rocks of the 
Kifelian type at Meux’s well and at Turnford, the probabilities appear 
to be in favour of these variegated strata belonging to the Poikilitié 
rather than to the sub-Carboniferous formation. 
The recognition of strata of Lower-Oolite age is anew, but not 
altogether unexpected fact, made known to us by the Richmond 
boring. Mr. Godwin-Austen was led by various considerations to 
regard it as probable that the great Paleozoic ridge had been sub- 
merged during a portion, at least, of the Oolitic period *. 
The particulars which we have now been able to ascertain con- 
cerning the nature and relations of the Great-Oclite strata exposed 
in the borings at Meux’s Brewery and at Richmond point to the 
following important conclusions :— 
(1) The Great-Oolite strata under the metropolitan area rest 
directly on the Palzozoic rocks, as at Meux’s Brewery, or on the 
Poikilitic strata, as at Richmond. In this we find an exact repeti- 
tion of the conditions found in the Boulonnais, where beds of probably 
Great-Oolite age rest directly on far more ancient deposits. 
(2) Both in the Boulonnais and in the metropolitan area, the 
whole of the beds of the Rhetic, of the several divisions of the Lias; 
and of the Inferior Oolite are altogether wanting. The absence of 
these formations was probably due to the circumstance that these 
districts and probably the whole area between them constituted 
dry land during the Rhetic, Liassic, and Bajocian periods. And 
this conclusion is confirmed by the manner in which the well-developed 
* See Quart. Journ. Geol. Soc. vol. xii. 1856, pp. 65, 71. 
