G 1. Granite, a protruded igneous rock.

SEA.

The above sketch (No. 6) represents a vertical section of the whole series of aqueous deposits in and around the Lake district.

DISTRICT OF THE LOWEST SLATES.

If a line be drawn in a direction from south-west to north-east, through Dent Hill and Saddleback, it will nearly coincide with the south-eastern boundary of these rocks, which occupy nearly the whole area between this line and the limestone hills of Egremont, Cockermouth, and Hesket Newmarket. Within this space granite appears in the valley of the Caldew; syenite in Carrock Fell; porphyritic dykes in High Pike; greenstone at Berrier, and in Binsey and other localities.

The granite of the Caldew is the lowest rock of the whole district, though probably of the most recent origin, for the veins which issue from it into some of the incumbent slaty beds, may be regarded as proof of its having been in a state of fusion since the date of their depositation. It is a compound of gray quartz, light coloured felspar, and black mica. Some portions have undergone decomposition to a considerable depth from the surface. Syningill and the channel of the Caldew exhibit its characters to advantage.

Above the granite, in Syningill, Mr. Ottley found a series of beds, of a nature almost intermediate between the granite and the ordinary slates. One of these is gneiss,—a laminated compound of quartz, felspar, and mica, traversed by veins of granite. Another is micaschist, a compound of silvery mica, in broad flakes, alternating with bands of quartz.

Above them, appears a thick series of dark slaty rocks, very regularly laminated, and full of black spots (hornblende?). This rock is locally called "whintin," and by geologists has been named hornblende-slate.

Still higher follows a thick mass of bluish argillaceous slate, full of distinctly crystallized prisms of "Chiastolite," which gives its name to the slate.

A great mass of slates follows, composing the principal part of the mountains of Saddleback and Skiddaw, Cawsey Pike, the Grasmoor Fells, and the

sides of Crummock and Lowes Water, and terminating in Dent Hill.

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These rocks are of a uniform argillaceous character, except where veins and thin laminæ of quartz diversify their aspect, or igneous rocks change the textures. The colour is usually dark, the surface glossy, and the mass divided into even or very undulated laminæ. Slaty cleavage" runs through a great part of the rock, but we believe good slate is rarely produced in this district, except at Bowscale Fell. Veins of lead occur in these slates at Dent Hill and on Lowes Water. Copper has been found in Skiddaw, and copper and lead, in various and beautiful combinations, occur in the mountainous group of High Pike and Carrock Fell, but the rocks of these localities may perhaps belong to the middle slate rocks.

No organic remains have yet been noticed in the dark Skiddaw slates. It is, nevertheless, possible they may occur, and yet may long escape detection, except the explorer finds the natural bedding of these rocks exposed by decompositions, or is aware of processes by which, even in solid slates, this bedding can sometimes be rendered evident. The observer should look for graptolites and small lingulæ or orbicula.

DISTRICT OF THE MIDDLE SLATES.

In proceeding from Borrowdale, through Langdale to Ambleside, and through Tilberthwaite to Coniston Waterhead, this great and complex series of rocks may be examined in an interesting variety of positions. By a short deviation from Borrowdale, over Sty Head, toward Wast Water, or from Langdale, over Hard Knott, to Eskdale, the granite which breaks into the midst of the series, and sends off porphyritic branches, and produces metamorphism of the slates, may be well studied.

The boundaries of the district occupied by the middle slates, are, on the north-west, the line from Egremont by Keswick, already mentioned; on the south-east,

a nearly parallel line from Broughton by Coniston Waterhead, Low Wood Inn, and the chapel in Long Sleddale. A part of the detached group of slaty rocks in High Pike (north-east of Skiddaw) may perhaps belong to this series; but they are much altered in aspect by the syenites and porphyries which there abound.

The base of the whole mass, as seen on Derwentwater, about Barrow, is a red mottled argillaceous rock usually regarded as a breccia. The colour being considered accidental, we find similar brecciated structures, and various gray tints, in the rocks at the entrance of Borrowdale, in those at the head of Ulleswater, around the north side of Grasmere, in the vicinity of Devock Water, and, indeed, generally through a great part of the area of the middle slates.

The fine-grained, gray, or green slaty rocks, like those of Langdale and Coniston Fells, are also of a derivative character, and only different by reason of the smaller size of the fragments which they enclose. The mottled aspect of some of these rocks has earned them the title of "rain-spot" slates (as at White Moss Quarry, near Ambleside).

Among these beds we find abundance of those porphyries composed of what seems indurated argillaceous matter, and imperfectly crystallized white felspar spots, melting away at their edges into the surrounding parts. Such as these occur under Helvellyn and about Thirlemere in great abundance, and may be recognised in the passage from Borrowdale to Wastdale, and from Langdale to Eskdale. These porphyries do not appear to be dykes forced in a melted state into fissures and cavities of the slates, but rather in some cases contemporaneous deposits, which have undergone greater alteration by heat than the associated strata, and deserve more than they do the title of metamorphic rocks. It is a confirmation of this view, that such rocks prevail around the great masses of granite and syenite of this region, and are yet distinct from the porphyritic "dykes," which are · branches from these masses.