326 



EEV, E. HILL ON THE BOCKS OF 



and with varying thicknesses, so nearly horizontal over so great an 

 area, with such a freedom from disturbance, can possibly be due to 

 anything except successive deposition, which, however, need not 

 necessarily have been subaqueous. The series bears an extremely 

 close resemblance to the hornblende -schists of the Lizard. I have 

 not, however, detected any of the " eyes " of felspathic material de- 

 scribed by Professor Bonney, nor such minute and perfect current- 

 bedding as is figured in his paper (Q. J. G. S. vol. xxxix. pp. 1-24). 

 He mentions there the suggestion that the schists may be altered 

 tuffs. Now if the question be asked, Can you show a source for the 

 material ? no answer can be given at the Lizard, but in Sark it is 

 possible to make a suggestion. The singular mass of intrusive rock 

 described in my paper on Guernsey as hornblende-gabbro is distant 

 from Sark only six or seven miles, and consists of materials closely 

 akin to these. Some of my specimens from Guernsey are scarcely 

 distinguishable from some specimens of the very black layers from 

 the beach at Port du Moulin, and the segregation-patches mentioned 

 above have much in common with the " sun-burned " patches of the 

 ' Birdseye/ I have not succeeded in finding any evidence of in- 

 cluded fragments or agglomeratic structure ; however, a distance of 

 six miles is enough to account for the absence of all but rather fine 

 materials. 



ISo cleavage exists, another point of resemblance to the Lizard. 

 About halfway down the valley which leads to the Creux Harbour 

 the usual K.W. dips are replaced for a few yards by a very steep dip 

 to the ISLE. ; thus there seems to be a roll. At the south side of the 

 Point Terrible the beds are crumpled just over a cave. On the south 

 side of the island of Brecqhou the beds show some contortions 

 about two or three hundred yards before they dip under the superior 

 rocks. The last two instances are only visible from a boat. All 

 these indicate a nip between east and west forces ; this agrees with 

 the structure of the Guernsey gneiss and the appearances in the rock 

 of Jethou. There are also some contortions which have different 

 directions in the bay | mile south of Port du Moulin and at the 

 vanishing point on the north-west coast. These may be owing to 

 either faults or intrusions, both of which are at hand in both places. 



3. The Creuoc Harbour Gneiss. — The directions of dip throughout 

 the hornblende-schist series, with exception of the brief roll just men- 

 tioned, are all more or less westerly, and, taken as a whole, radiate 

 from the easternmost point of the island. Accordingly on the 

 eastern side we should seek for the base of the series *. We find 

 it. Let the visitor just landed on the pier detach his eyes from the 

 singularity of the scene, and scrutinize the southern side of the cliff- 

 wall which encircles the spot. He will see about halfway up the 

 face a group of horizontal stripes, which subsequent examination 

 shows to be part of the hornblendic series. But the rock beneath 

 these is of entirely different aspect, homogeneous and massive. 



Examined in hand-specimens this lower rock is highly crystalline, of 

 moderate coarseness. It consists of pink and flesh-coloured felspar in 

 * Prof. Liveing places the lowest beds at Port du Moulin. 



