148 PROCEEDINGS OF THE GEOLOGICAL SOCIETY. [Nov. 29, 



1500 feet thick : it rests on the crystaUine chloritic schists described 

 at the beginning of the paper (p. 144). The dip of all the beds of the 

 carbonaceous series at San Pedro de Cova is E.N.E. ■§ N. 45°, which 

 corresponds with the dip of the fossiliferous slates of Vallongo ; the 

 country between the two places is a rough mountainous district, with 

 little vegetation ; the outcrop of the beds is seen everywhere, and their 

 relative position does not admit of doubt. 



The coal is worked by inclined shafts which follow the dip of the 

 beds, the deepest of which in 1844 was about 600 feet ; at that time 

 I was informed that about 4500 tons of coal were raised annually, 

 which are consumed principally in Oporto. The prices at the pit's 

 mouth were then about equal to 6s. Sd., lbs. and 25*. per ton for the 

 three qualities into which it is sorted : the carriage by land to Oporto 

 costs about 6s. 3d. per ton. 



The coal is an anthracite of very pure quality, containing very little 

 bituminous matter. 



The same beds of coal have been opened on a smaller scale on the 

 north bank of the Douro at Jeremunde, about twelve miles above 

 Oporto, and they have been traced from that spot to San Pedro de 

 Cova, but they are nowhere so thick as at the latter place. North 

 of San Pedro de Cova this whole carboniferous series thins away very 

 rapidly, and the beds die out completely about a mile and a half 

 north of that place, thinning off agamst the crystalline rocks of the 

 Serra de Vallongo, which there project considerably to the eastward 

 of their principal line. Where the Oporto road crosses the Serra de 

 Vallongo, the fossiUferous clay-slates of Vallongo, No. 3, rest imme- 

 diately on the crystalline micaceous and chloritic schists ; and, as far 

 as I observed, the same is the case along the whole course of the for- 

 mation to the northward of Vallongo. It appears that the carboni- 

 ferous series No. 4 is a very local deposit, only found to the south- 

 ward of the road from Oporto to Vallongo, and which attained an 

 unusual development, under some peculiarly favourable circumstances, 

 in a deep bay left in the granitic chain near San Pedro de Cova. It 

 would be interesting to trace out the course and character of the 

 coal-beds on the south of the Douro, but this I believe has never 

 been done. 



(b.) Section along the Brag a road. 



The slate formation is developed on a smaller scale to the north- 

 ward of Vallongo. Where it is crossed by the road from Braga to 

 Oporto, the following series of beds is exposed in descending order : — 

 Sienite reaching to two miles south of Villa Nova de Famelicao ; then, 



1 . Coarse red micaceous sandstone, which becomes more and more 

 slaty in the lower beds. 



2. Black carbonaceous shale, with some beds of coarse grit and 

 also of clay iron-stone : nearly perpendicular with a strike of N.N.W. 

 The spot where the road crosses these beds is called Terra Negra. 



3. The above pass into a soft grey clay-slate, cleavage perpendicular, 

 striking N.N.W., followed by soft slates of various light colours, with 

 some alternations of slaty sandstone and of indurated ferruginous 



