AUSTEN — TERTIARY DEPOSITS OF THE SUSSEX COAST. 57 



formed elliptical shingle, or that of large subangular blocks ; the 

 rocks of the granitic series are much the most rounded, some pre- 

 senting beautifully smooth and polished surfaces ; the greenstones, 

 though their angles are worn, retain much of the forms resulting 

 from the jointed structure of those masses. On the other hand, 

 many of the blocks are sharp and angular, as is particularly the case 

 with respect to the quartz and slate rocks. 



In size these older materials range from coarse shingle up to masses 

 of 20 tons weight ; the granitic blocks, which are by far the most 

 numerous, are also of larger dimensions than the others. Fragments 

 of greenstone are to be met with from 3 to 4 feet in length. A 

 rounded block of porphyritic granite has recently been exposed near 

 Pagham, by coast-line denudation, at a spot which only a very short 

 time since formed part of a cultivated field ; this block measures 

 2/ feet 5 inches in circumference. 



It is difficult to define the precise area over which such materials 

 as these, so foreign to the rock-formations of the district, have been 

 distributed, but they will be found wherever the yellow-clay-gravel 

 occurs : they have a wide range beneath the whole of the level ex- 

 tending towards Selsea, locally known as the Man-wood, being met with 

 in the formation of water-courses, and other works. Guided by the 

 coast-section, these materials, either taken numerically or according to 

 their bulk, seem to be most abundant and characteristic in that por- 

 tion of the accumulation between Bracklesham Bay and Worthing : 

 their apparent increase about the Selsea peninsula may perhaps, how- 

 ever, be owdng to the advance which the coast-line there makes. 



Rounded blocks of large size also occur as far inland as north of the 

 South Coast Railway, and certainly beyond the limits of the yellow- 

 clay gravel-deposit ; they are there covered over by beds of a series 

 which will be presently described. At one time I imagined that the 

 presence of these granitic boulders indicated that the beds in which 

 they occurred belonged to one and the same period, and that the 

 altered character of the beds which contained them was the result of 

 accumulation under shallower water conditions than the yellow-clay 

 gravel-beds : such, however, I have since ascertained is not the case. 

 In many instances where large blocks occur amidst beds which in the 

 coast-sections overlie the yellow-clay-gravels, they have served to 

 protect from denudation small patches, subjacent to them, of the 

 characteristic accumulation in which they were originally deposited : 

 in these positions the larger blocks are outliers, shomng the former 

 extent of the yellow-clay gravel-beds ; and they may also serve as 

 a measure of the moving power of the water, which when it denuded 

 that area was insufficient to displace the larger masses. The great 

 rounded boulder at Pagham is a good illustration of the relative force 

 of this denudation, which will be further alluded to. 



The smaller water-worn specimens of old or of crystalline rocks 

 are of various sizes, such as may be met with on the beaches of the 

 French or English coast of the western extremity of the Channel ; 

 and coast-line materials may, we know, be conveyed to great 

 distances. The formation of perfectly rounded shhigle, however, 



