82 J. A. Birds — Geology of the Channel Islands. 



along the shore, the syenite is interrupted by veins of the horn- 

 bleudic granital. It does not extend far inland, but is soon replaced 

 by the mass of hornblendic granital constituting the north of the 

 isle. 



Of the felspathic portion of Guernsey I have nothing to remark, 

 more than that it furnishes magnificent crystals of felspar, especially 

 in Moulin Huet and Petit Bot Bays, surpassing in size and brilliancy 

 of colour any in the porphyritic granites of Cornwall, or Shap Fell, 

 Cumberland. The cliffs are frequently intersected by veins of 

 greenstone and felstone running both parallel with', and at right 

 angles to the apparent bedding or jointing of the syenite. The 

 hornblendic portion of the island also occasionally {e.g. at St. 

 Sampson's) affords splendid crystals of black hornblende, finer 

 indeed than any I have ever seen in England or Scotland. The 

 principal veins in this portion are of felstone, serpentine steatite, 

 and epidote, of which last I found some rather pretty crystals im- 

 bedded in quartz. Chlorite frequently occurs in tlae form of coatings 

 and stains. 



The principal axis of elevation of the whole area of the islands is 

 said by Prof. Ansted to run W.N.W. and E.S.E., and is regarded by 

 him as a continuation of the great east and west elevations affecting 

 the Continent of Europe, which are best illustrated in the range of 

 the Alps and Pyrenees.' 



The little island of Sark consists of syenite, with similar veins, as 

 in Guernsey, of greenstone, felstone, serpentine, steatite, etc., and of 

 hornblendic rocks, along with porphyry and trap. The hornblende 

 is said to occupy the extreme ends, and to form a belt across the centre 

 of the island, while the felspathic syenite fills up the intervals. The 

 axis of elevation here, and also in the little islands of Herm and 

 Jethou, between Sark and Guernsey, is nearly at right angles to 

 the axis of the latter, or N.N.E. and S.S.W., and corresponds, says 

 Ansted, rather with recent elevations and depressions than with the 

 original upheaval.^ 



I was not fortunate enough to find any, or at least good specimens 

 of the minerals with which Sark is said to abound. The old mine- 

 heaps appear to have been thoroughly ransacked, and the shores are 

 inaccessible except at a few points ; only on the beach at Epercherie 

 — the original landing-place — I picked up specimens of fine black 

 hornblendic porphyry containing well-defined crystals of felspar, 

 and a few pebbles of agate and jasper, generally much decayed, as 

 well as some of serpentine, and a green mineral, which I take to be 

 actinolite. The vein of kaolin, stained purple and pink, crossing 

 the north side of the Coupee, is very conspicuous. Dr. MacCuUoch, 

 in his map of the island, indicates three other veins, — 1, of quartz, 

 chalcedony, jasper, and agate ; 2, talcose schist with steatite ; 3, 

 chlorite with pyrites; crossing the Coupee parallel with the kaolin. 

 None of these are visible from above, one side being covered with 

 detritus, and the other plunging down perpendicularly into the sea. 



1 Ansted and Latham's Channel Islands, pp. 256, 260. 



2 Ibid, p. 263. 



