110 



Mr. D. Sharpe on the Geology of 



studied very conveniently in the cliffs opposite to Lisbon, where the following 

 observations were principally made. Unfortunately, the lowest beds are not there 

 exposed, and they vary so much in thickness and appearance, within very short 

 distances, that a stratigraphical table of the formation cannot be completed from 

 observations made elsewhere. 



The following is a tolerably correct list of the beds in the cliff, near Almada : 



Feet. 

 Yellow calcareous sand, containing a few 



shells 50 



Limestone, full of shells 2 



Marly sand of a bluish colour, containing 



oysters, pectens, &c 10 



Limestone, full of casts of shells 2 



Blue marl, with many shells 6 



Sandy limestone, ditto 1 



Yellow sand, containing Echini, and a few 



shells 10 



Greenish sand, with few shells ; in this bed 

 small quantities of quicksilver have been 



found 10 



Brown clay 3 



Blue clay, with thin layers of shells (b). ... 30 

 Sands and limestones, which I had no oppor- 

 tunity to observe accurately, as they occur 



where the cliff is inaccessible 50 



Sandy limestone 3 



Carried forward .... 177 



Feet. 



Brought over 177 



Limestone, full of shells 1 



Sand 2 



Limestone, full of shells 3 



Sand 10 



Rubbly limestone, with oysters and other 



shells 5 



Sand, containing calcareous concretions. ... 4 



Rubbly limestone, few shells 4 



Hard limestone, many shells 10 



Sandy limestone, a bed of oysters 5 



Yellow sand, some oysters 12 



Sandy limestone 3 



Yellow sand, few shells 12 



Sandy marl, ditto 6 



Sandy limestone, pectens, &c 12 



Yellowish sand, with a few fragments of shells 40 



Yellow marly sand, with few shells 12 



Sand, containing some mica 13 



In all about 331 



This table is incomplete at both ends ; very little is wanting above it — I 

 cannot say how much is wanting below. 

 ■ At Adica the uppermost beds consist of 



Yellow calcareous sand 10 feet. 



Blue sandy marl, with many shells 20 — 



the latter resting upon a calcareous bed. If these strata were placed at the top of 

 the preceding list, the upper part of the formation would probably be completed ; 

 the blue marl of Adica would then correspond with that of the valley of Piedade 

 to the S.E. of Casilhas, where the uppermost beds cannot be distinctly seen. 



The most marked stratum of the series, is the blue clay (6) mentioned near the 

 middle of the table ; but this bed is in some places so thin as not to be easily re- 

 cognized. Were it thought convenient to separate the formation into parts, the 

 most natural arrangement would be 



Upper Limestones and Sands, 



Blue and brown Clay, 



Lower Limestones and Sands ; 

 but as some species of shells occur both above and below the clay, the subdivision 

 would not be of much value. 



