72 REPORT—1848. 
Lugnaquilla, 3000 feet above the sea. On both flanks of the granite rests a series 
of sedimentary deposits whose general strike is N.E., dip S.E., and therefore oblique 
to the granite, which cuts them all in succession ; the oldest of these rocks are at the 
north end of the east flank of the granite, and consist of sandy and slaty beds altogether 
from 4000 to 5000 feet thick (‘‘ Barmouth Sandstones”). These are followed by 
argillaceous beds, and volcanic ash and breccia with contemporaneous greenstone ; 
a considerable number of fossils have been found in these beds, the equivalents of the 
lowest of all the Silurian remains in Wales. On the western flank of the granite only 
this upper series is found. Both series of sedimentary rocks have been upheaved, 
subjected to lateral pressure, contorted and fractured; besides which, they have all 
been altered along the line of contact with the granite to the extent of 5000 or 6000 
feet, and over a breadth of half a mile on the surface; the influence of the formerly 
heated granite is shown in alteration of structure, and in the production of minerals 
not existing in the unaltered rock; in the conversion of sandstone into quartz-rock, 
and of the volcanic beds into a crystalline hornblendic rock. The dip of the slate, 
&c. is sometimes 70°, but usually much less; the granite extends under them, and 
is shown again at a distance by denudation ; portions of the altered slate remain upon 
several summits of the granite hills, and show the original height of the surface of 
the granite, which in these points has been preserved from the rapid decomposition 
which has wasted it all around. The summit of Lugnaquilla is a mass of slate of this 
kind, traversed by numerous large veins of granite ; similar veins pierce all the rocks 
in contact with the granite, and many of these, having taken the direction of the 
bedding of the rock, appear as if interstratified. In Glen-malur these granite veins 
may be seen extending with parallel edges for hundreds of feet. Besides these and 
the contemporaneous greenstones, there are numerous dikes like the Cornish Elvans 
in the southern and metalliferous part of the county; these never cut the older sedi- 
mentary rocks, but abound in the upper series. Glen-malur, in which several lodes 
of lead are worked, is formed by a great fault; and there are several other nearly 
parallel glens, some occupied by lakes; the Vale of Avoca is also caused by a fault 
which shifts all the lodes; these dislocations extend into the granite itself. In Wick- 
low there are no formations newer than the lower Silurian, except the drift; but a 
little westward the edges of the Silurian rock are covered by the conglomerates and 
sands of the Old Red system. The drift consists of clays and sand mixed with lime- 
stone boulders, which are scratched and furrowed; in some parts of it organic remains 
occur in such a manner as to prove they lived on the spot; some of the species how- 
ever are Arctic, and occur 700 feet above the present level of the sea. In the north- 
ern part of the county the drift is gravelly and mixed with angular fragments of older 
rocks adjoining; huge blocks of granite and quartz-rock are strewed over the county, 
the lower surface occasionally retaining distinct scratches and furrows. The surface 
of the county appears to have undergone extensive denudations since the deposit of the 
drift, and many of the ravines and caldron-shaped hollows are quite free from drift. 
On the Drainage of a Portion of Chat Moss. 
By G. W. Ormenop, M.A., F.G.S. 
The surface of the moss varies from 80 to 100 feet above the sea-level; the bottom 
at the deepest part proved, is at least 100 feet below the sea-level. Part of this moss 
is now being laid dry by means of open drains, under the direction of M. Ormerod. 
After cutting the drains, the level of the peat falls rapidly; near the main leader it 
sunk perpendicularly 5 feet 6 inches in about nine months; -and in one part 2 feet _ 
6 inches in a single week. 
Lieut.-Colonel Portlock communicated some observations on apparent changes in 
the level of the coast near Portsmouth, and contended that as these evidences of sub- ~ 
sidence could be traced back to the most ancient times, so they had continued up to 
the present day, and expressed his conviction that a parallel might be found in exist- — 
ing nature to all the phenomena of ancient times. It appears that part of Fort Cum- | 
berland near Portsmouth stands on a bank of gravel and sand, and that owing to some ~ 
new groins made to protect it from the sea, a fresh direction was given to the tide, and 
a portion of the bank undermined and washed away, in the course of which a thick 
