PORTLAND EOCKS OF ENGLAND. 207 



feet. This reminds us at once of g, especially as seen in the last 

 erosion, and is no doubt its continuation ; for upon it we find a 

 creamy limestone similar to li, whose thickening in one direction and 

 dying-out in the other may here be traced. This, again, is followed 

 by the representatives of the earth and the brashy limestone i and 

 h, here full of Cyprids. The blocks at the base are, in one or two 

 cases, of large size, containing Cerithium porilayiclicum ; and there are 

 rolled fragments of Kimmeridge (?) Clay ; but usually they are only 

 small white stones, and the limestone becomes compact towards the 

 top. The thin- splitting ferruginous rock follows for about 1 foot ; 

 and then succeeds a line of laminated dark earth between two 

 lighter bands ; and over all comes 3 or 4 feet of flaggy limestone, 

 which may be, but is not proved to be, the same that overlies the 

 basal sands at the north and south extremities of the eastern 

 section. But the extraordinary series of local deposits is not yet 

 exhausted; for the ferruginous beds {I) which disappear to the south, 

 when traced northward come to a bank, against which they end, 

 and have derived blocks on the slope at their base. This bank is 

 formed by first another dark clay band like i, and then by A,-, a 

 mass which is rubbly towards the base, but calcareous towards the 

 top, and has a limestone band in the middle. All here is covered 

 by the dark sandy soil referred to the Lower Greensand. 



"We have now to determine where among these deposits the 

 Portland rocks end, and thereby to learn the nature and circum- 

 stances of formation of the upper beds of that series. The section 

 given in the Geological-Survey Memoir of the N.E. quarry shows 

 that, while d and e are considered Portland, /is considered Purbeck. 

 That of the western side makes ?', or Z, or m the first Purbeck bed, 

 according to the part of the quarry it is supposed to be taken from ; 

 while h is said to contain Trigonice, and the/ on this side is called 

 Portland Limestone, because of the nodular fossiliferous masses it 

 contains. Mr. Brodie's section, however, makes h contain PIcmorhis, 

 and reckons it as Purbeck. I certainly saw no Trigonice in h, nor 

 any thing but impressions of small shells, except on the east side, 

 where the Pcdudime occur. I could find no freshwater fossils in/; 

 but its general behaviour, lying in hollows, and being filled at its 

 base with derived Portland blocks and small stones, proves its 

 unconformity to the Portland, and that it was deposited under 

 circumstances that are only to be found in the Purbeck. On the 

 other hand, d is undoubtedly Portland by its fossils; and, as a 

 matter of fact, all the fossils found in the actual beds above g are 

 freshwater, all those of the beds below d are marine. As for e and 

 /, they attach themselves to d both actually and in their range ; and 

 yet e is a calc-tufP, like the usual base of the Purbeck, and both 

 appear to be unfossiliferous. Their character, therefore, at present 

 is doubtful, and we must draw the upper line of the Portland either 

 above / or above d ; in the latter case it would certainly be easy to 

 obtain a block of which the upper part would be Purbeck and the 

 lower Portland. This inclines me to include the two in the 

 latter. 



