H. 8. Jevons — The Breidden and Berwyn Rocks. IS 



I may add that the first specimen I saw during an ascent of Monte 

 Eotondo was a huge boulder, or hloc percM, perhaps 12 to 15 feet 

 in diameter, at a height of 5,000 to 6,000 feet on a narrow spur of 

 the peak, the interior of which reminded me of an ant's nest in an 

 old oak beam, and so completely was it honeycombed that I was 

 able to penetrate into the heart of the mass, where I was practically 

 invisible to my companion. 



Can any geologist suggest a cause for this extraordinary and, both 

 in altitude and area, widely distributed erosion ? It can hardly be 

 decomposition, for, in the specimen described above, the rock seems 

 in good condition just beneath the outer surface, and, at any rate in 

 some instances, the situation appears to make the action of sand 

 very improbable. Neither Professor Bonney nor I have seen any- 

 thing in the Alps at all comparable to it, nor remember to have 

 read a description of its occurrence in other places. 



Note. — Since writing the foi'egoing my attention has been drawn, 

 through the kindness of the Editor and of Dr. C. I. Forsyth Major, 

 F.Z.S., to a passage at pp. 127-128 of "La Corse," by M. Ardouin- 

 Dumazet, forming the lith series of a ''■ Voyage en France." This 

 writer very accurately and pictorially describes the extraordinary 

 weathering or erosion of the 'Red Granite,' or granitoid rocks of the 

 Calanche, but only briefly alludes to the hollowed out, bomb-like 

 forms specially referred to by me, if indeed they may be recognized 

 in the phrase "La forme la plus generale de ces bizarreries est un 

 evidement en forme de niches." He also speaks of "Des silhouettes 

 d'animaux fantastiques." 



As already stated, the rock from which my specimen was taken, 

 instead of on the spot as it ought to have been, was at some distance 

 to the south-west of the limited region of the Calanche, and, though 

 much eroded or undercut, was probably of a different geological 

 character from the sometimes almost spherical, bomb-like blocks such 

 as that in the stream near Porto. I am inclined to think that the 

 Calanche themselves are a rose or brick-coloured granite, as the 

 writer just quoted and Joanne's " Guide en Corse" state them to be. 



EXPLANATION OF PLATE II. 

 Fig. 1.— Eroded dome, " Tete de Chien" (8 to 10 feet long), "Le Calauclie," near 



Piana, west coast of Corsica. 

 Fig. 2. — Eroded boulder in stream near Porto, west coast of Corsica. 



IV. — Note on the Keratophyres of the Beeidden and 

 Berwyn Hills. 



By H. Stanley Jevons, M.A., F.G.S., Lecturer in Mineralog-y and Demonstrator 

 in Geology in the University of Sydney. 



IT may be of interest to note the occurrence of a somewhat rare 

 and interesting rock, named Jceratophyre, at two easily accessible 

 localities in a district where it has been hitherto unknown — at 

 Moel-y-Golfa, in the Breidden Hills, and in the Berwyn Hills. 

 The Breidden Hills. 

 Moel-y-Golfa was visited by me in 1899, and I collected a few 

 specimens, which, however, remained unexamined until a few days 



