Though here called limestone, this series of beds is, indeed, only partially and variably calcareous. The strata of limestone are much intermingled with beds of shale, and the uniform dark colour of the group renders it somewhat difficult for an inexperienced eye to distinguish between them. Veins of calcareous spar are frequent in the small cracks of the thicker beds; the cleavage planes, which pass through the shales, are somewhat interrupted and twisted in the band of limestone; and the effect of atmospheric action is different on the argillaceous and calcareous strata.

The organic remains are numerous, including corals, brachiopoda, tentaculites, and trilobites. There may be collected about twenty species in a quarry by the roadside from Coniston Waterhead to Ambleside, about two miles from Coniston. Among these are the chaincoral (Catenipora escharoides), Orthis flabellulum, Orthis grandis, Isotelus gigas, and other trilobites. At Low Wood Inn, also, similar collections may be made, but the country near Coniston Waterhead appears most productive.

Ireleth Group.-Above the Coniston limestone is a thick series of dark flaggy slates, such as occur at Kirby Ireleth, south of Broughton, on the road from Coniston to Hawkshead, between Low Wood Inn and Bowness, in Kentmere, in Long Sleddale, and at the Crook of Lune, under Howgill Fells. This part of the series yields roofing-slate at Kirby Ireleth, near Ulverston, and flags near Ambleside, and at crook of Lune. In a district farther east, at Horton in Ribblesdale, Yorkshire, the valuable flag-quarries, which appear to be of this series, are well worthy of a visit. The surfaces of the flags (surfaces of stratification, not cleavage) are there undulated by nodules, enclosing orthoceratites, lituites, and favosites. They somewhat resemble the flags of Llandeilo, in South Wales.*

* And still more closely, as Professor Sedgwick has shown, the flags of Denbighshire, in North Wales.-Proceedings of the Geological Society, 1845.

Organic remains are not commonly observed in this group of rocks, except in the vicinity of the limestone bands, at or near its base. Some columnar joints of crinoidea were collected in it, on the shore by Bowness Ferry, on Windermere, by the author, in 1837.

Howgill Group.-A more arenaceous series than the last upon which it rests, though in both sandy and argillaceous deposits alternate, the sandy layers being more frequent, often thicker, and perhaps of coarser grain in this. There are no important conglomerates, and no remarkable brecciated rocks in the group. It is not in general subject to any other metamorphic appearance than that caused by slaty cleavage, which is less remarkable, and less productive of good slate, than in the lower group. Organic remains, if they occur, are

very rare in these rocks.

Kirkby Group, the highest and most fossiliferous of all the series of Cumbrian slaty rocks. In it the true slaty cleavage is but a little developed; the rocks grow more and more micaceous upwards, and gradually exchange bluish and gray tints for purplish and reddish hues. By these characters the series approximates to the more recent class of strata-the old red sandstone, which succeeds, and is superimposed. In fact, the upper portion of the Kirkby group is undistinguishable from the fossiliferous tilestone which occurs in Caermarthenshire, and is there classed by Mr. Murchison as the lower member of the old red sandstone. These circumstances are nowhere better observable than in the banks of the Lune, above Kirkby-Lonsdale, and on the line of the old Kendal road from that town. The fossils from these localities were collected by the late Dr. William Smith and the author in 1822-4, and described in a communication to the Geological Society in 1827. But the number since added by Mr. Danby and the diligent naturalists of Kendal from Benson Knot, Brigsteer, and other localities near Kendal, is much greater, and the whole series demonstrates perfectly the affinity of these upper micaceous flags and slates to the Upper Ludlow

slates and tilestone beds of Shropshire and Caermarthenshire. Very few dykes of any rock or igneous origin are met with in this series of strata, except in the vicinity of the remarkable granitic mass of Shap Fells. This fills a considerable area, perhaps equal to that occupied by the granite under Skiddaw. It occupies the crest of high bold ground, about three miles west-southwest of Shap Wells, and is traversed by the road from Penrith to Kendal. The rock is quite unlike either of the sorts of granite already mentioned. It is porphyritic granite; a compound of gray and reddish felspar, quartz, and dark mica, in grains of small or moderate size; but amidst these are scattered large and fine crystals of reddish felspar, one inch or even more in length. In this it resembles some of the trachytic products of the Rhenish volcanoes. By this character, and some other peculiarities, the Shap granite may be recognised in hand specimens, and still more perfectly in the numerous boulders of this rock which have been scattered by ancient surface forces, on wide areas in the north of England, and to distances even as far as the Chalk Cliffs of Yorkshire. The granite of Ravenglass and Devock Water is also recognisable, and has been identified in loose fragments and scattered blocks as far south as the plains of Cheshire.

THE GRANITE.

The circumstance that there are three granite masses of different mineral characters, raised to the surface in three unconnected tracts of the small area of the Lake Country, is interesting; but that these three sorts of granite should be found one in each of the three divisions of the slate rocks which exist in this district is surprising. There is, probably, no other such case known; and we ask—is the character of the granite due to the influences exercised on its consolidation by the slates with which it is associated? or must we ascribe to some

peculiar conditions, coinciding with each period, the periodic characters of the granite, as to other conditions, we ascribe the periodic characters of the slates? According to this latter view, which is by far the most probable, and which might be supported by many and strong analogies, the three granitic masses are of three different ages. According to observations made in the vicinity of each-observations proving that the slates in contact have been altered by the heat, and injected by the ramified veins of the fused rocks-each is of more recent date than the strata with which it is associated, but we have no certain proof of their relative antiquity; no decisive argument to bring against the supposition, that the granite of the Caldew, though it is in contact with only the lowest slates, may be of a date later than the highest of them. In confirmation of this supposition, we may remark that the whole of the region of the slates is elevated upon an axis passing north-east and south-west through the northern part of the district; that this axis passes through the valley of the Caldew and that the appearance of the granite there is connected with, and is in fact dependent on, the disruption of the slaty rocks along the line of fracture. If this granite, therefore, was of later consolidation than the fissures which it fills, it may be regarded as of more recent origin than the whole of the slaty series; but the proof of this is imperfect. For the granite sends veins only into the immediately superincumbent gneiss; and the hornblendic and chiastolitic slates must have derived their metamorphosed aspect from a more pervading action of heat than that which emanated from the fused granite forced into an anticlinal fissure.

;

FIRST GREAT DISTURBANCE OF THE SEA-BED.

Such are the strata and the rocks of igneous origin which compose the central area of the Lake district. To complete their history, we must consider the nature of the movements by which they were raised from

their original place on the sea-bed, put into new positions, and exposed to new conditions.

Old Red.

No. 7.

Old Red.

Upper Slates. Middle Slates. Lower Slates. Granite. Middle Slates.

There is one general movement of this description, traceable in the Lake district, which occurred after the deposition of the whole slate series, and before the production of the strata next in the order of succession. This movement was one of general elevation, on an axis ranging from south-west to north-east through Grasmoor Forest and Skiddaw Forest. On this line the

lowest slates are thrown up; in the part where its effect is greatest, the subjacent granite appears. On each side of the axis some of the middle slates appear, and on the south side the upper slates. These latter are concealed on the northern side by the over-extension ("unconformability") of the superincumbent strata; and it is this unconformability of the two orders of deposits, which proves the movement of disturbance to have occurred in the period of geological time which intervened between them.

Similar movements of the old slate rocks happened at the same period in nearly parallel directions in the range of the Lammermuir Hills, raising the whole line of country from St. Abb's Head to Port Patrick. The greater ranges of the Highlands, on lines nearly parallel, were elevated at the same period; and the same remark applies to considerable tracts in the north-west of Ireland. Round all these tracts the slates are unconformably covered by old red sandstone, as in Cumberland and Westmorland.

No. 8.

Axis

P