THE GEOLOGIST. 
very extensive, extending over more than three-fourths of the whole 
island. Their strike is within a few degrees of N.E. and S.A\^. — 
that is, parallel to the mountain-range — but the direction and inten- 
sity of their dip is very various. Sometimes they dip seaward, as in 
the north of Douglas Bay ; at other places they dip landward, as in 
the south of Douglas Bay ; and in other localities, again, they dip in 
an intermediate direction, as in about the centre of Douglas Bay. 
The average intensity of the dip of these rocks is very great. At Dou- 
glas it varies from about 70° to 90°. At Langness it is from about 60° 
to 80° ; and at Port St. Mary, still further south, it is almost equally 
great. At the foot of Garrachan, in the centre of the island, it is 
from 50° to 60°, Upon these and numerous other similar data I 
have founded my estimate of the thickness of these rocks. Their 
composition and texture is also very varied. In contact with the 
granite, they are " completely metamorphosed, passing regularly 
through the stages of a gueissose rock and mica-schist into clay- and 
grauwacke-schist." In the centre of the island they are chiefly mica- 
slate ; near Peel they form a good roofing-slate ; at Spanish Head 
they are so fibrous and tough as to be extensively quarried in lengths 
of six or eight feet for piles, door-posts, chimney-pieces, etc. ; and 
about Douglas they become hard and splintery, and are much used 
for building purposes. In most of these rocks the cleavage is very 
imperfectly developed, and in others it does not appear at all. 
These rocks are exceedingly rich in metals — copper, lead, silver, 
zinc, etc., being obtained. Several veins of lead and copper are 
profitably worked. The mines at Laxey, about halfway between 
Douglas and Eamsey, are especially noted. The vein runs nearly north 
and south, and " contains copper-ore, lead-ore rich in silver, varying 
from eighty to a hundred and twenty ounces in the ton of lead," 
and an ore of zinc, locally termed " Black Jack." To drain these 
mines a monster wheel, 72 feet 6 inches in diameter, stated to be the 
largest wheel of the kind in the world, is employed. Another mine, 
nearly equally important in its operations, is worked at Foxdale, near 
Peel. The lead obtained from this locality also contains a large 
amount of silver, though not nearly so much as is obtained from the 
Laxey ore. A third very extensive mine for copper and lead is 
worked on Brada Head, about one mile from Port Erin, in the S.W. 
of the island ; and numerous otlier mines of greater or less impor- 
tance have been in operation at different times. Many of these are 
now abandoned, but it is more from the lack of funds than from the 
exhaustion of the metals. This want of necessary funds has also 
prevented the opening of new veins of great richness which are 
known to exist. Whether the quartz-rocks associated with this 
series contain gold is a question of practical importance which we do 
not here pretend to solve. Having, however, a due regard to the 
generalizations of Sir lioderick Murchison respecting the gold-bear- 
ing rocks, and to the experience of the last few years in various parts 
of the world, especially in Xorth Wales and other parts of the British 
Islands, it seems to us as not at all improbable that a careful search 
