1848.] SHARPE ON THE GEOLOGY OF OPORTO. 149 



clay. These beds reach to the banks of the river Ave at Barco da 

 Trofa, v^^here they rest on a soft chloritic slate ; strike N.N.W. : a 

 little south of Vend a da Serra this rests on granite. 



(c.) The section crossed by the road from Yianna to Oporto pre- 

 sents the same features as the above. It appears that throughout the 

 whole course of the formation the three upper divisions of the forma- 

 tion, sandstone, carbonaceous shale and clay-slate, are everywhere to 

 be distinguished ; but that the lower carbonaceous division is not to 

 be found north of Vallongo. There is everywhere to be seen a 

 gradual passage between the beds of the different divisions, which 

 leaves no doubt that the whole are to be regarded as subordinate 

 parts of one formation. And the great similarity in mineral cha- 

 racter between the black carbonaceous shales No. 2, in the middle of 

 the formation, with the beds associated with the coal in the lowest 

 division No. 4, farther connects the whole together. 



(C.) RoadfroiYi Opoi'to to Aveiro. 



A similar series of Silurian rocks is seen about thirty miles to the 

 south of the Douro, on the road from Oporto to Aveiro : after leaving 

 the granite of Oporto the road crosses brown micaceous and argilla- 

 ceous schists, the foliation of which strikes N.W., and dips S.W. 80°. 



Granite, with occasional peaks of sienite. 



Gneiss ; dip of the foliation S.W. 30°. 



Micaceous schists alternating with gneiss ; dip of foliation S.S.W. 

 from 60° to 80°. 



Sienite at Villa da Feira. 



Micaceous and chloritic schists striking W.N.W., which continue 

 to Ovar, beyond which place the Silurian slates are seen in the follow- 

 ing ascending series : — 



3. Clay-slate, strike N., dip of cleavage E. 80° varying to S.E. 80°, 

 of considerable thickness. 



2. Carbonaceous shale which lies over the preceding near Estareja, 

 and alternates with red slaty sandstone, dip S.E. 60°, dip of cleavage 

 S.E. 80°. 



1. Red slaty sandstone. 



Beyond Angeja these beds are covered up by a thick deposit of 

 coarse gravel which conceals the strata over the great plain round 

 Aveiro. 



From the direction taken by the Silurian slates, they ought to cross 

 the high road from Oporto to Coimbra near the banks of the Vouga ; 

 but beyond the southern termination of the micaceous schists near 

 Albergaria Nova, the whole country is completely covered with gravel, 

 which reaches to a red sandstone seen on the banks of the Vouga 

 near Sardao ; so that we are left in doubt whether the slates are con- 

 tinued in this direction. 



The red sandstone of Sardao is a fine-grained freestone in thin 

 beds separated by partings of red marl, resembling the new red sand- 

 stone of our Midland counties ; it dips S.E. 5°, and is overlaid to the 

 southward by sands which belong either to the oolitic or cretaceous 



