1888.] of the rocks of Guernsey. 385 



nothing below them is known anywhere. Yet, coarse as is this 

 Guernsey gneiss, it generally possesses a structure, whether we call it 

 foliation or cleavage ; and not unfrequently contains thin slaty parti- 

 tions which can hardly be anything except beds. In some places the 

 bedding can be ascertained with certainty, in others with consider- 

 able probability. The foliation can generally be made out, and 

 agrees with the bedding where this can be seen. I have examined 

 and registered these appearances along nearly the whole of the 

 coast, and also at one or two points of the interior. The results 

 are as follows. 



The most northerly point where true gneiss appears on the 

 east shore is in the rocks beneath Castle Cornet and the Castle 

 breakwater. These are much shattered and veined and intersected 

 by numerous dykes, so that the bedding is both variable and 

 indistinct : it can however be seen at several places. At the end 

 of the breakwater the dip is W. (steep): under Castle Cornet N.W. 

 or N.N. W. (very steep), and at the middle of the pier, N.N.W. 60°. 

 From the bathing-places I have noted dips both N.E. and N.W. : 

 other signs show that the rocks are here much crushed and shat- 

 tered. At the mouth of the tunnel there is seen a south dip, 

 caused by a roll over of a few yards extent; and a similar roll 

 may be seen on the shore in Petit Fort Bay, but the general dip 

 seems N.N.W., about 45°. Going southwards it remains the same 

 in direction, but under Kent Battery is very slight in amount, 

 and continues to be only some 10° or 20° until within a few yards 

 of Fermain Bay. Thus the gneiss from Fermain Bay northwards 

 has a general northerly dip which though varying somewhat both 

 in direction and magnitude if continued must make it finally 

 plunge beneath whatever formations may be found beyond. 



At Fermain Bay, or rather a few yards to its north, an abrupt 

 change takes place. A quantity of dioritic rock seems to intrude, 

 and the dips hitherto gentle with an E.W. strike alter suddenly 

 to a vertical position and a strike N.S. This general character is 

 maintained by them all the way to Jerbourg Point: the dip is 

 generally W. and at one point as little as 60°, but is usually almost 

 vertical. Sometimes it even leans over to the E. Similarly along 

 the whole of the south coast, from Jerbourg to Pleinmont, where- 

 ever bay or cleft permits the coast to be reached, wherever quarry 

 or crag enables the structure to be examined, there if a strike be 

 seen that strike is almost always northerly, if bedding can be 

 deciphered the dip is always steep. The following are my latest 

 and most carefully taken notes : Moulin Huet ; strike of foliation 

 N.N.W. vertical, bending at end of bay to W. vertical : Saints 

 Bay (here there are strong indications of bedding) strike N.N.W., 

 dip 60° or 70° E.N.E. and, at the mouth of the bay, N, 80 W. : 

 Icart Point, strike, N.N.W., dip steep E.N.E. : a quarter of a mile 



