455 



The rock of Le Roule, near Cherbourg, is stated by Mr. Clarke 

 to present to the eye two lines of fracture, "one parallel to the horizon 

 the other nearly perpendicular to it ; and from these with the lines of 

 dip and direction the fragments assume their forms. '' 



The author then offers some remarks on the probable effects of 

 crystalline action in the first place, and of subsequent forces in the 

 second. Veins of a light ochre colour traverse the beds of Le Roule 

 from top to bottom ; whilst other veins and threads of pure milk-white, 

 opaque quartz, sometimes studded with crystals, range through them 

 in a direction from S.E. to N.W. where the general dip of the beds 

 is from N.E. to S.W. at an angle of 30°. This direction of the veins 

 precisely agrees with that of the transverse fissure or ravine through 

 the Montagne du Roule, the latter also ranging from S.E. to N.W. 



This transverse rectangular direction of the ravine, Mr. Clarke 

 says, corresponds with the mechanical effect of elevation, and may be 

 compared to the case of Corfe Castle in Purbeck, where the nearly 

 vertical beds of hard chalk have been fractured at right angles. 



The memoir concludes with a general recapitulation of the struc- 

 ture and phenomena of the Cotentin, and a comparison of them in 

 other countries. 



