516 Notices of Memoirs—On the Hiatus in West Cork. 
(10 inches) one finds the amount of compression which has taken 
place (18:5). The argument is the same as that used by Dr. Sorby 
for the bed of quartzite folded in the slate of Devonshire. 
TlL.—On vue Istanp or TorGHATTEN. 
By Professor W. J. Soruas, M.A., F.R.S.E., F.G.S8. 
HE author described the results of a visit which he made to this 
island in July, 1880. The platform from which the peak 
of the island rises is a narrow plain of marine denudation, pro- 
duced when the island was submerged 875 feet below its pre- 
sent level. The tunnel which traverses it is a sea-cave excavated 
between two master-joints. The floor of the cave is covered with 
angular blocks of gneiss, which have fallen from the roof since 
the elevation of the cave-floor above the sea-level; the blocks 
have fallen far more rapidly at the entrances of the cave than 
in the interior, and, as a consequence, the roof rises from the 
middle towards each end of the tunnel, and so does the angular 
debris, which thus forms at each entrance a vast sloping mound. 
The vast quantity of fallen material is an interesting indication 
of what has been- accomplished by simple mechanical disintegra- 
tion since the island was raised above the 375 feet level. The 
joints are the most important factors in denudation; excepting 
moutonnéed faces, the author considers most of the bare rock faces 
which constitute the surface of Northern Norway are merely ex- 
posed joint planes. He has seen joints in the same rock, and 
having the same direction, extending from a few feet to over a 
thousand, and surface features in parallelism with them from a 
facet not a yard across to precipices over a 1000 feet high. 
TVY.—On tHE Hiatus sAaID TO HAVE BEEN FOUND IN THE Rocks 
or West Cork. 
By G. H. Kinanan, M.B.1.A., 
President of the Royal Geological Society of Ireland. 
(ae paper was commenced by a table of the different classifica- 
tions of the Cork Rocks. 
GRIFFITH. JUKES. Hott. 
Carboniferous Slate. Carboniferous Slate. Carbone 
i Coomhoola Grits. 
Yellow Sandstone, Upper Old Red Sandstone. Kiltorcan Beds. 
Old Red Sandstone. Lower Old Red Sandstone. Glengariff Beds 
Silurian. Glengaritt Grits. (Silurian.) 
From the table it is apparent that although using different 
group-names Griffith’s and Jukes’ classifications are essentially 
similar, while Prof. Hull’s classification is materially different from 
both; although by adopting for his new groups, names very similar 
to those of Jukes, a careless reader might suppose his classification 
was similar to that of Jukes and Griffith. 
The paper went on to point out that the supposed hiatus rested on 
