17i 



TiiE GrEOLOaitsT. 



very extensive, extendiDg over more than three-fourths of the whole 

 island. Their strike is within a few degrees of K.E. and S.W. — 

 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 yery 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, silyer, 

 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 

 miues 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.AV. 

 of the island ; and numerous other mines of greater or less impor- 

 tance have been in operation at diff"erent 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. AVhether the quartz-rocks associated with this 

 series contain gold is a question of practical importance which m o do 

 not here pretend to solve. Having, however, a due regard to the 

 generalizations of Sir Eoderick 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 



