130 Mr. D. Sharpe on the Geology of 



2ndly. Tlie position of the red sandstone upon the older rocks (Sections 9, 11 and 13), proves that 

 these were again elevated after the deposition of the Espichel limestone. 



Srdly. The position of the Almada beds upon the red sandstone at the end of the Serra de San Luiz 

 (Sect. 1), shows that the sandstone had been much elevated before the tertiary period. 



Lastly. The tertiary Almada beds have been much elevated all round the older chains ; their usual 

 dip being about 30°, but at Palmella it is 50° (Sec. 9), and at the foot of the Serra de Vizo nearly 80° 

 (Sec. 13). 



The forces which elevated this district acted at each period in the same direction along an anticlinal 

 line ranging S.S.E. from the castle of Palmella. A considerable fault, crossing the red sandstone between 

 Cezimbra and Cabo de Ayres, forms the western limit of these elevations, and has divided the neighbour- 

 hood of Cezimbra into two districts of disturbance. The dislocating agents are not visible on the east 

 of the fault, but to the westward the trap-rock described at p. 127 rises at the northern foot of the castle 

 of Cezimbra, elevating the Espichel limestone and the red sandstone to a great angle (Section 12). From 

 this spot to Cape Espichel the same formations continue to dip highly to the north ; and from the position 

 of the beds, it is probable, that some other eruptive rocks may be found at the foot of the cliffs west of 

 Cezimbra, which I had not time to visit. On the beach on the west side of Cezimbra are some large 

 blocks of sienite, which could not have come from far, and which were probably derived from the foot of 

 the cliffs further on. 



All these disturbing forces had ceased to act before the deposition of the upper tertiary sand which 

 was deposited when all the other strata formed a surface similar to that we now see ; the only alteration 

 which has affected this formation being that which has raised it above the level of the sea without breaking 

 its original horizontality. 



Superficial Detritus. 



The valleys near Lisbon are often lined with detritus washed down from the hills 

 inclosing them, but I did not see any of those accumulations of foreign materials 

 which we have been accustomed to call diluvium. Some of the limestone hills, 

 especially about Bellas and Loures, have been very much channeled by water, and 

 the top of one hill near the latter village is covered by isolated rocks, several feet 

 high, of limestone still remaining in situ, but worn into rounded masses separated 

 by deep channels. This may have taken place during the tertiary period, for there 

 is no evidence that the district has been washed over, since the deposition of the 

 tertiary formations, by any of those immense bodies of water of which we see so 

 many traces in other countries. 



APPENDIX. 



On the Earthquake of 1755. 



The physical effects of the great earthquake which destroyed part of Lisbon in 

 1755, have been very much exaggerated. The accounts of the great loss of life 

 and destruction of property carry away the imagination, and lead us to think the 

 geological action of the earthquake much greater than it really was. A large 

 part of the present town consists of houses erected before the catastrophe, and of 



