10 PROCEEDINGS OP THE GEOLOGICAL SOCIETY. [NoV. 21, 



phsenomena presented by the Kentish Town well must be taken into 

 consideration in connexion with his ingenious hypothesis*. The 

 exact state of the question remains, however, yet to be decided. No 

 satisfactory proof of these beds belonging to the New Red Sandstone 

 group has hitherto been met with. In mineral character they cer- 

 tainly closely resemble the Red Marls, and unless some proof on 

 other grounds can be adduced to the contrary, it is a point in 

 favour of such a correlation. 



As it is well known that the Gault in some places passes into a red 

 clay, I at first considered it possible that these strata might be the 

 result of a like change, but the great thickness of the beds and the 

 alternations with sandstones militate against that view. Secondly, I 

 would remark, that near Dorking the Lower Greensand is capped by 

 a local bed of bright red clay ; but it is only 8 feet thick, and there- 

 fore the same objection holds, although the possibility of such a 

 variation is indicated. Next, with regard to the Weald clay : there 

 is here no objection with regard to dimension, and the occurrence 

 of mottled red clays and subordinate sandstones is a common feature 

 in this deposit ; still the absence of all freshwater fossils does favour 

 this correlation. With respect to the evidence obtainable from 

 organic series in these red beds, if the nature of the work, at so 

 great a depth and so far out of reach, did not present an unavoidable 

 source of error, we have evidence such as might solve the difficulty 

 presented by mineral characters. Several fragments of apparently 

 cretaceous Ammonites and Belemnites have been brought up by the 

 auger, but it may be doubtful whether those may have fallen down 

 the sides of the bore-hole. Still, on the other side, it is to be ob- 

 served that no such fossils were found in the Gault itself, and that the 

 bore-hole is tubed to the depth of 1172 feet ; and M. Jus, who has 

 superintended this work, and carefully noted the occurrence and posi- 

 tion of the fossils, informs me that it was in one bed especially, viz. 

 the pebble bed (No. 40 of the sectional list, p. 13), at a depth of 1 158 

 feet, that a small Belemnite was particularly abundant, and that in 

 one case the fossil was imbedded in sandstone and not loose. For 

 the last week all the fresh clay has been carefully washed and sifted, 

 but no more fossils have been found. 



Mr. D. Sharpe has had the kindness to examine these fossils, 

 and the following are the remarks he has made upon them : — 



"17 Soho Square, 16th November 1855. 

 " My dear Sir, — Among the fragments of organic remains from 

 the Artesian well at Kentish Town, there are very few which admit 

 of even a conjectural determination, and only one which can be 

 named with certainty; this is the Ammonites infiatus. Sow., which 

 also passes under the name of A. rostratus ; the specimen is suffi- 

 ciently large and perfect to show all the distinctive characters of the 

 species, viz. a strong keel, back broad, sides flattened, with strong 



* Still, admitting such a possibility, the Lower Greensand must range up to the 

 flanks of this ridge, and might, therefore, nevertheless be found underground at 

 othe? points at or near London, beyond the interference of the central axis. 



