560 Notices from the Minute Boohs of the Geological Society. 



same agent having operated on both formations en masse. The rock of Le Roule 

 presents to the eye two Unes of fracture, one parallel to the horizon and the other 

 nearly perpendicular to it, and these, with the lines of dip and direction, produce, 

 the author says, the peculiar outline of the fragments. This structure, Mr. Clarke 

 considers, is due to the arrangement of the component particles in the first instance, 

 and to subsequent agents in the second ; and he is of opinion the phsenomena 

 prove distinctly the truth of Brongniart's assumption, that these are crystalline and 

 not mechanical rocks. If, he adds, heat was an agent in consolidating these beds, 

 and electrical action was connected with it, the tendency of the strata to assume 

 their characteristic features might be accounted for. Other cases of slates as- 

 suming a regular form are mentioned in the paper, particularly one at Boppart, on 

 the Rhine, where the cleavage yielded six-sided tables, somewhat similar to the 

 fragments previously mentioned. (Fig. 3.) 



Fig. 3. 



Fragment of slate from Boppart, on the Rhine. 



The transverse ravine of Le Roule is shown to agree precisely with the strike of 

 veins of pure white quartz, which intersect the strata from south-east to north-west ; 

 and Mr. Clarke observes, that this direction of the ravine corresponds with the me- 

 chanical effect of elevation ; and he dwells at some length on this not being a local 

 phsenomenon, but connected with a widely extended operation. The transverse 

 break through the beds of hard chalk at Corfe Castle, on the coast of Dorsetshire, 

 is considered as probably connected with the ravine at Cherbourg ; and he proceeds 

 to state, that if the observer extend his researches to Calvados and Brittany, and 

 thence to Devonshire, Weymouth, Purbeck, the Isle of Wight, the Weald of Sussex 

 and Kent, and the Boulonnais, he would be induced to connect some of the most 

 striking phaenomena of these districts with probably a contemporaneous series of 

 events. 



The decided similarity of the Devonshire schists and granite with those of the 

 French coast ; the similar protrusion of the granite at an epoch much posterior to 

 the production of the slates ; the occurrence of highly inclined beds from the oolites 

 to the tertiary series along the coast of Dorset, dipping, like the rocks of the Co- 



