ON THE DEEP BORIIN'G AT RICHMOND, SURREY. 525 



give angles of about 30°. This is the case with the lowest cores 

 brought up in this boring. 



By some this high dip, and the necessary inference of uncon- 

 formable relation between these variegated strata and the overlying 

 Jurassic and Cretaceous rocks, may be regarded as telling in favour 

 of their pre-Carboniferous age. But it is by no means impossible 

 that Poikilitic strata in this area were disturbed and denuded before 

 the period of the deposition of the Great Oolite. The lowest beds 

 exposed in the boring are certainly much more like those of the 

 Xew Red than of the Old Red. It must be remembered, too, that in 

 Northamptonshire somewhat similar variegated strata have actually 

 been found intercalated with the Carboniferous series. It cannot 

 fail, however, to be a constant subject of regret to geologists that 

 no more precise evidence concerning the age of these strata was 

 obtained. 



With respect to some other strata passed through in this well, 

 interesting additional evidence has been obtained since the reading 

 of the paper. 



At the depth of 704 feet in this well we indicated the existence 

 of a curious conglomerated chalk, covered by 15 feet of hard chalk. 

 The former was referred to the Zone of Belemnites plenus in its 

 remanie condition ; and the latter, it was suggested, might not im- 

 probably be referred to the '-'Melbourn Rock" of Mr. A. J. Jukes- 

 Browne. Since the reading of the paper, we have been indebted to 

 Mr. William Hill, Jun., E.G.S., of Hitchin, for a number of facts and 

 specimens which prove conclusively the identity of the Melbourn 

 Rock with that which occurs at. this horizon under Richmond. 



Mr. Hill, who had long studied the microscopic characters of the 

 different beds of the Chalk series, and had traced the different zones 

 through a large part of the Midland area, on reading our account of 

 the conglomerated chalk of Richmond, at once sought for it along 

 the line of outcrop of the Melbourn Rock, The specimens he has 

 kindly submitted to us prove that a precisely similar bed everywhere 

 forms the base of the Melbourn Rock of the Midlands, and that there 

 is the strongest resemblance in microscopic characters between that 

 rock and its conglomerated base in the district he has studied and 

 in the London basin. The recognition of this important horizon 

 cannot fail to greatly facilitate the separation of different zones in 

 the Chalk in this country. 



With the aid of Dr. Hinde, F.G.S., and Prof. T. Rupert Jones, 

 F.R.S., we have further investigated the interesting specimens of 

 chalk-marl obtained from the Richmond well. On dissolving the 

 chalk-marl in dilute acid, a residue, amounting in some cases to no 

 less than 50 per cent of the whole, is left behind. By washing this 

 residue many beautiful specimens of fossils have been obtained. 

 Portions of the spicular mesh of hexactineUid sponges are common, 

 and in some cases Dr. Hinde has been able to determine the genera 

 and species. Very abundant, indeed, in some cases are silicilied 

 prisms of the shell of Inoceramus ; these sometimes, indeed, make 

 up a large part of the mass of insoluble residue of the chalk-marl. 



