Physical Structure and older stratified Deposits of Devonshire. 665 



To the east of Looe, a section from tlie coast to the nearest granite exhibits 

 on the whole a descending series ; yet we do not think that any of the beds of 

 such a section ought to be placed at a lower geological level than the lowest 

 slaty group of South Devon. 



In the cliffs west of Looe there are many fine green^ chloritic slates_, alter- 

 nating with greenish quartzose beds^ penetrated by quartz veins^ which have 

 a prevailing dip about S.E. by S. But at Ore Point is a striped rock, with 

 numerous red and green bands, alternating with coarse green, quartzose 

 beds, much penetrated by white quartz veins. The dip is reversed to a point 

 about N.N.E., and is not less than 70° or 80°; and some of the beds have a 

 true slaty cleavage inclined towards the same point, but at an angle of not 

 more than 50°. The coarse striped beds, sometimes alternating with bands 

 of nearly pure quartz (very instructive, from their mineral structure, and from 

 a number of poor mineral veins nearly parallel to a series of north and south 

 joints), are continued nearly with the same inclination to Polparrow. At the 

 entrance of Polparrow Harbour, the coarser quartzose beds are overlaid by a 

 beautiful rock, with a perfect transverse cleavage, producing a fine-striped 

 slate. The beds dip north, at a great angle, while the cleavage planes dip 

 also north, but at a much smaller angle. Examples of this kind occur very 

 rarely in South Wales ; and we never remarked a similar case in the North 

 of England ; for whatever be the inclination of the beds, the cleavage planes 

 are generally inclined at a greater angle*. 



As the same prevailing northern dip is continued to the mouth of the Powey 

 river, it is obvious that the beds above described are inferior to the fossil- 

 iferous group. 



Similar indications of a northern dip are seen in a part of the coast section 

 on the east side of St. Austell Bay. Commencing a section at Greber Head, 

 and continuing it from thence through the head of St. Blazey Bay to the gra- 

 nite, we have the following order : 



1. A series of quartzose and chloritic beds, continued to a cave under Combe Farm, with a 

 prevaiHng dip towards the south. At that place there are large east and west joints, perhaps 

 marking the presence of a fault ; and beyond them the dip is reversed to magnetic north. The 

 same phenomenon is also seen about a quarter of a mile south of Polkeris. 2. An ascending 

 series, with a northern dip at a great angle, continued to Polmere Cove, where there appears to be 

 a great break among the strata t> The fossiliferous slates are in the lower part of this group. 



* On the coast west of Padstow we found a still more remarkable example, viz. a calcareous 

 slate, dipping unequivocally at an angle of 40°, intersected by true horizontal cleavage planes, 

 producing a beautiful striped slate. 



t Somewhere near the line of break, and probably connected with it, is a great channel of 



