two Sections in the BrickfieW, Copford, Essex. 431 



locality, where the straight horizontal layers of limestone, 

 and beds of blue clay, alternate from the bottom to the top of 

 those cliffs, in precisely the same manner as the blue clay and 

 fine sand alternate here. It matters not that one is a marine 

 deposit, and the other a fresh-water one : the laws of nature 

 are in both instances the same. 



Excepting two species of Valvata, a whole shell is very 

 rarely to be obtained from this deposit ; but in my last visits, 

 I obtained, with a little trouble, the following: — Lymneus sp. ; 

 imperfect, but, by the large size of the fragments, apparently 

 stagnalis. L. glutinosus Turt. Valvata obtusa Tart. V. sp., 

 not figured in Turton's work. Paludina sp., the only species 

 of this genus found fossil here. -\w lo snoiteionoo 3sh adT 



Mineral Characters of the Boulders found in the Stratum 

 No. I. of each Section. — Flints, both rounded and angular, 

 with chalk fossils ; quartz sandstone ; milky crystalline 

 quartz ; granular crystalline quartz of that kind termed Druid 

 sandstone ; micaceous sandstone ; quartz sandstone, with 

 crystals of felspar ; very beautiful conglomerates in boulders ; 

 compact felspar, with crystals of felspar (porphyry). 



Your correspondent Mr. Morris observes, in IX. p. 264., 

 that the existence of the chalk nodules in the blue clay at 

 Copford is an interesting fact, as he (Mr. Morris) has only 

 found them at Grays, in the beds above that stratum. The 

 blue clay containing the nodules of chalk at Copford lies so 

 far above the chalk formation, that that stratum has not been 

 penetrated in sinking wells, in the surrounding neighbourhood, 

 to from 50ft. to more than 100 ft. deep; but the occurrence 

 of these nodules in sinkings of not more than 20 ft. below the 

 surface was, I thought at the time, an indication of the chalk 

 basin being shallower just at this spot than at other places ; or 

 that we have chalk near the surface somewhere in this neigh- 

 bourhood. (VII. 437, 438.) It would be an important dis- 

 covery, indeed, if we could find it out; not only in a geolo- 

 gical, but in a commercial view ; for chalk is an article in 

 high request here for our siliceous soils. But it is certain, that 

 the chalk nodules which I have in my cabinet, as procured from 

 the Copford brickfield, from its blue clay bed, could not be 

 bouldered from our nearest chalk locality (Ballingdon), in 

 water, without being dissipated in the transport. If I have 

 misunderstood Mr. Morris's observation respecting the blue 

 clay bed at Copford, I beg to say that it is a fresh-water de- 

 posit upon the London clay ; and, therefore, it is interesting to 

 find specimens of soft chalk in it. 



Stanway, near Colchester, Essex, May 19. 1836. 



liMool aril in $IaK>9qa9 iud \ noUfiDm bluoo I > 



1 1 4 



