AND ASSOCIATED ROCKS OF ANGLESEY. 



41 



aspect, the northern edge of the largest patch in Anglesey, 

 according to the map. But on reaching this we find it a mass of 

 gabbro, generally rather coarse — considerably altered, no doubt, but 



Tig. 1. — Junction of Schist and Serpentine. 



A. Schist. B. Serpentine. C. Sand. 



unmistakable. There is, however, a small inconspicuous outcrop of 

 true serpentine, separated from it by some grass, about seventy yards 

 to the north of its eastern end. Prom the west end of this gabbro 

 massif we made* for the shore. Here we found an irregular rocky 

 coast-line fringed with skerries and islets, mostly dry at low tide. 

 Some are schist, marvellously contorted, others gabbro, a few ser- 

 pentine. "Without a large-scale map, it would be impossible to 

 make the details intelligible; but it may suffice to say that we 

 worked carefully along the shore to the inlet by Tyddyn Gob, 

 examining the different rocks. In one place the evidence, though not 

 perhaps absolutely conclusive, seemed strongly in favour of the serpen- 

 tine being intrusive in the schist ; for if the junction were due to a 

 fault, this would be a very strange one (fig. l)f. Further on (beneath 

 a wall) gabbro is seen intrusive in serpentine, which has assumed, 

 as is not uncommon in such eases, a locally schistose aspect. A 

 large mass of gabbro forms an island near here. On the bank 

 of an inlet near Tyddyn Gob is a rather schistose rock, which in 

 the lower part resembles a foliated gabbro, in the upper a schist. 

 Purther to the south the schists are wonderfully contorted, and 

 there is a small mass of serpentine near Ty Ucha (reached by 

 crossing a causeway over an inlet); this is greatly crushed and 

 slickensided. Appearances suggest an intrusive junction ; but both 



* On my first visit to this place I was accompanied by Mr. F. T. S. Houghton, 

 to whom I am much indebted for kind help on this and a subsequent occasion. 



f In the face of a crag facing S.E. and rising from the shore about the top of 

 the letter e in mile on the map. 



