36 



J. PRESTWICH ON THE QUATERNARY PHENOMENA 



however, down the cliff to where the rock has been quarried near 

 the fissure, the old beach, covered by the light-coloured loam, is found 

 to abut against an old cliff of Lower Purbeck strata, the upper part 

 of which is doubled back, and its debris thrown over the loam and 

 carried southward, as shown in the following section (fig. 4). 



Fig. 4. — Section of Raised Beach and Old Cliff at the top of the pre- 

 sent cliff on the west side of Portland Bill. (See also Sect. 4, 

 PL I.) 



d. Angular debris, 4 feet. d'. Light-coloured loam with seams of debris and 

 angular blocks ; land and freshwater shells in places : 11 feet. e. Raised 

 beach with very large pebbles at base, 7 feet. 



This overlapping mass of debris extends all over the line of old 

 cliff, which it has levelled with the surface from this point to its 

 termination near the Sand-holes on the east cliff. To the south- 

 ward it gradually thins out as it recedes from the old line of cliff, 

 and ranges seaward over the old beach ; but still it is clearly trace- 

 able in places as far as the land-mark at the extremity of the Bill, 

 where it mixes with the upper part of the old beach. 



This bed of rock-debris is remarkable from the circumstance of 

 its containing, with specimens of the unfossiliferous beds of the 

 Lower Purbecks of Portland, abundant fragments of the fossiliferous 

 beds of the Middle Purbecks, none of which now exist in situ in the 

 island. In it I also found a number of fragments of the thin seams 

 of fibrous carbonate of lime (known by the quarrymen as "beef"), and 

 of the so-called cinder-bed, which consists of a concreted dark mass of 

 small oysters (so common in the Lul worth and Up way Purbecks), 

 Portland flint, fossil wood, and Tertiary iron sandstone. Mr. Ethe- 

 ridge has kindly determined for me the following species* : — 



* My friend Mr. Osmond Fisher, who was therewith me, considers they may 



