218 SUPEEPICIAL DEPOSITS. 



considerably greater depth before the rock is reached. In 

 Guernsey there are apparently instances where a considerable 

 depth of clay overlies a raised beach, and has again a layer of 

 rolled stones on its upper surface. The rolled stones of the 

 beaches in Jersey, as in Guernsey, are, so far as I have 

 observed, derived from underlying or adjacent rocks. In one 

 bed, however, one of those included in the clay, I found a few 

 well rolled pieces of flint. Flint pebbles, it may be observed, 

 occur on our present beach, on the east and south-east of the 

 island, and as I have already suggested,* they may probably 

 have been derived from the denudation of the chalk of the 

 neighbouring part of France. Bonnissent has remarked on 

 the large proportion of flint pebbles in the quarternary deposits 

 of the Departement de La Manche,f and suggests that the 

 chalk formation was probably much more extensive there 

 before the quarternary period, and that great denudation 

 probably took place during the subsidence of this part of 

 Europe. 



In Jersey the yellow clay, brick clay, or brick earth 

 extends irregularly all over the island, here and there absent, 

 and in many places deposited to a great depth. It is found 

 over the greater part of the high plateau ground as well as on 

 the low-lying land ; it stretches out to sea under the sand of 

 our shores, and caps some of the islets of the coast. It is well 

 developed on many hill-sides and slopes, and often attains 

 great depth in depressions or pockets on the high ground, as 

 well as on some parts of the level low-lying land on the coast. 



It is a more or less clayey loam, varying from a loam to 

 a highly plastic clay, generally fine in grain, but sometimes 

 coarser from admixture of disintegrated granite or diorite. 

 On microscopic examination the grains are generally found to 

 be rounded. The colour is yellow, mostly of a light shade, 

 but it is sometimes darker, with a brown or reddish tinge ; here 

 and there it effervesces with a mineral acid, at least in one 

 locality. It contains " race " — fantastically shaped concre- 

 tions resembling the Mannchen, or Pvppchen of the German 

 Loss. 



The clay is generally unstratified, but occasionally distinct 

 bedding in fine layers is observed. For example, below the 

 raised beach on the St. Clement's Road, which I have 

 described, where the slope reaches the low ground, there are 

 two sections shown, one on each side of a narrow lane, which 

 show a good example of stratification in fine laminae, alter- 



* Op : cit. 

 t " Essaie Geologique sur le Departement de la Manche," p. 383. 



