cleavage, on which it depends, is very general in all the mass of rocks, which are some thousand feet thick, both in Wales and Cumberland. In both districts also the sedimentary rocks are much intermixed with porphyry and greenstone, both in seeming beds and dykes, and many parts of the slaty rocks themselves are really amygdaloidal, or else composed of fragments of porphyry and other igneous rocks. No organic remains have been found in the Cumbrian district, but they occur in Snowdon. Thickness, in Cumberland, 6000 feet at least.

Clay-slate.

LOWER OR CUMBRIAN GROUP.

This is a singular uniform inass of laminated argillaceous rock, of a dark colour and smooth texture, with vertical cleavage and symmetrical joints. It is devoid of organic remains.

Chiastolite-slate differs hardly at all from the preceding, except by including crystals of chiastolite and hornblende.

Hornblende-slate.

This is very different from the rock so named in Glen Pitt, for its basis is clay-slate, with intermixed crystals of hornblende or actinolite. These three divisions may be about 3000 feet thick in Cumberland.

Passing through the series ascendingly, there is little occasion for remark in relation to the lower division. The actinolite is only a variety of the hornblende, which forms the slate called after it, a mineral which occasionally presents fine radiating fibres, and has hence been named after its resemblance to the sun's rays. The chiastolite imbedded in clay-slate, and comprising one of its varieties, is so called from the form of an X, in dark lines, visible on the summits of the crystals. The chiastolite-slate, a soft, dark kind, occurs near Bareges in the Pyrenees; at St. Jago di Compostella in Spain, and in the Sierra Morena; at Agnavanagh in Wicklow; and constitutes in connection with other varieties the great mass of Saddleback, 2787 feet high, and of Skiddaw, 3022 feet, in Cumberland.

Snowdonia, a range of variously coloured and indurated argillaceous slates, the lower division of the Cambrian group, is of peculiar interest to the Geologist; for here we meet

with the first extant monuments of organic life, which have not hitherto been discovered in the Cumbrian district, though the same strata are there extensively developed. The division includes the high mountains of Carnarvonshire and Merionethshire, where the slates are abundantly interstratified with masses of porphyry; and where south Britain has its loftiest elevation, Snowdon rising to the height of 3557 feet. In this series of strata, both in Wales and Cumberland, the richest metalliferous veins occur, excepting the lead and iron ores of the carboniferous system. Greenwich Hospital receives a large revenue from the estates of the unfortunate Earl of Derwentwater, transferred to that establishment upon their forfeiture to the crown, and which abound in productive lead ore. Corresponding strata in Brittany and the Hartz are also highly metalliferous. The upper components of the system, the Bala limestone, consisting of a vast thickness of dark laminated beds in Wales, present many fossil remains of a few species, but none have been found in those patches of the strata which occur in Westmorland. The Plynlymmon Rocks, hard, slaty, fine or coarse-grained, occupy the greatest part of the chain of the Berwyns, of which Plynlymmon is the central mass. They have few metallic riches, and appear to be nonfossiliferous.

The whole region of the slates exhibits a magnificent physiognomy, having been largely invaded by the igneous rocks, which have variously elevated the strata, and burst through them in great masses, or flowed into them, forming inter-stratifying layers and dykes. "Supported by granite," says Phillips, "and mixed with igneous masses, the slaty rocks of the English lakes rise to more than 3000 feet in height, and present a variety of outline and intricacy of combination which, in connexion with clear lakes and considerable waterfalls, leave to Switzerland little superiority." At Burrowdale, Scawfell, Patterdale, and Helvellyn, the slate is associated with greenstone, amygdaloid, and argillaceous porphyry, which constitute the towering crags and lofty precipices of those districts, and form the rocks over which the cataracts fall. The contour of Snowdonia exhibits a similar style of landscape, and indicates the amazing energy with which disturbing causes have acted upon it, the intruding porphyries here, as in Brittany, Cornwall, and in the Lammermuir Hills on the southern boundary of the plain of the Lothians, having been subject to subsequent disturbance equal to that of the strata. "We began a toilsome march," says Pennant, speaking of his ascent of Snowdon," clambering among the rocks. On the left were the precipices over Cwm (valley) Brwynog, with Llyn (the pool) du yr Arddwy at their foot; on our right were those over the small lakes Llyn Glas, Llyn y Nadroedd, and Llyn Coch. The last is the highest on this side of the mountain, on whose margin we were told that, in fairy days, those diminutive gentry kept their revels. This space between precipice and precipice forms a short and no very agreeable isthmus, till we reached a verdant expanse, which gave us some respite before we laboured up another series of broken crags; after these is a second smooth tract, which reaches almost to the summit, which, by way of preeminence, is styled y Wyddja, or the conspicuous. It rises almost to a point, or, at least, there is but room for a circular wall of loose stones, within which travellers usually take their repast.

"The mountain from hence seems propped by four vast buttresses, between which are four deep cwms, or hollows: each, excepting one, had one or more lakes lodged in its distant bottom. The nearest was Ffynnon Llas, or the green well, lying immediately below us. One of the company had the curiosity to descend a very bad way to a jutting rock that impended over the monstrous precipice, and he seemed like Mercury ready to take his flight from the summit of Atlas. The waters of Ffynnon Llas from this height appeared black and unfathomable, and the edges quite green. From thence is a succession of bottoms, surrounded by the most lofty and rugged hills, the greatest part of

whose sides are quite mural, and form the most magnificent amphitheatre in nature. The Wyddfa is on one side; Crib y Distill, with its serrated tops, on another; Crib Coch, a ridge of fiery redness, appears beneath the preceding; and opposite to it is the boundary called Lliwedd. Another very singular support to this mountain is Y Clawdd Coch, rising into a sharp ridge, so narrow as not to afford breadth even for a path."

Pennant proceeds to remark :-"The view from this exalted scene is unbounded. In a former tour I saw from it the county of Chester, the high hills of Yorkshire, part of the north of England, Scotland, and Ireland; a plain view of the Isle of Man ; and that of Anglesey lay extended like a map beneath us, with every rill visible. I took much pains to see this prospect to advantage; sat up at a farm on the west till about twelve, and walked up the whole way. The night was remarkably fine and starry; towards morn the stars faded away, and left a short interval of darkness, which was soon dispersed by the dawn of day. The body of the sun appeared most distinct, with the rotundity of the moon, before it rose high enough to render its beams too brilliant for our sight. The sea, which bounded the western part, was gilded by its beams, first in slender streaks, at length glowing with redness. The prospect was disclosed to us like the gradual drawing up of a curtain in an amphitheatre. We saw more and more, till the heat became so powerful as to attract the mists from the various lakes, which in a slight degree obscured the prospect. The shadow of the mountain was flung many miles, and showed its bi-capitated form; the Wyddfa making one, Crib y Distill the other. I counted this time between twenty and thirty lakes, either in this county, or Meirionydd (Merioneth) shire. The day proved so excessively hot, that my journey cost me the skin of the lower part of my face before I reached the resting-place, after the fatigue of the morning.

"On this day the sky was obscured very soon after I got up. A vast mist enveloped the whole circuit of the mountain. The prospect down was horrible. It gave the idea of a number of abysses, concealed by a thick smoke, furiously circulating around us. Very often a gust of wind formed an opening in the clouds, which gave a fine and distinct vista of lake and valley. Sometimes they opened only in one place; at others in many at once, exhibiting a most strange and perplexing sight of water, fields, rocks, or chasms in fifty. different places. They then closed at once, and left us involved in darkness; in a small

space they would separate again, and fly in wild eddies round the middle of the mountains, and expose, in parts, both tops and bases clear to our view."

But Snowdon-the Saxon translation of the Welsh for snow-mountain-with the ranges in connexion with it, acquires peculiar interest, from its presenting us with the dawn of organic life in the world which we inhabit, as far as extant monuments serve to unfold it-the morning twilight of the era of living beings, which broke immeasurable ages be

fore the present epoch. Professor Phillips speaks of having found, himself, in the slates of Snowdon, Zoophyta (lamelliferous corals) and Brachiopodous (arm-feet) bivalves. The latter are mollusca, so called from having two long, spiral, fleshy arms, or brachia. The above specimens he obtained from Snowdon in the year 1836.

"It may surprise," he observes, "the speculators in cosmogony to hear that these, the

most ancient forms of life known to us, should be, not plants, but animals; not merely zoophyta, but conchifera; not the lowest grades of their respective classes, but perfectly developed lamelliferous zoophyta, and brachiopodous mollusca." These mollusca, now extinct, lived in the ocean attached to other bodies. They prevail through the older fossiliferous rocks, in connection with a large increase of species, gradually disappear from the sphere of existence in newer formations, and finally vanish in the lias, where only

one species occurs. In addition to these fossil examples of ancient organisms, traces of Annelidans, the first class in Cuvier's arrangement of articulated animals, have been recognised. These are worms with red blood, formed of rings, or annular segments, like the leech and common earthworm, some of which are naked, while others have a shelly covering, or are protected by a kind of coat formed of agglutinated sand. Their remains are abundant in more recent deposits, but in several instances, upon the older rocks, their traces only are discernible. "Singular convoluted impressions," Mr. Murchison remarks, " had been observed by the Rev. A. Oliphant, of Llampeter College, on the surface of the building-stone of that place; and upon submitting some specimens to the examination of Mr. W. Macleay, that profound naturalist pronounced them to have been formed by sea-worms." The engraving represents the instance in question, Nereites Cambrensis, from Llampeter in North Wales, from which the body appears to have been composed of about one hundred and twenty segments. A greater number of segments appears to have distinguished a more slender species, named after the founder of the Cambrian system, Nereites Sedgwickii.

Such were the creatures that appear to have first crawled upon the stage of life, opening that drama of being in which we are now actors, and in which man, as poet, warrior, and sage, has for some thousands of years played a conspicuous part. Wandering upon our sandy shores, we often in listlessness or idle curiosity overturn the stones in our pathway, and observe existing Nereidina-slender worms wriggling in the water and mud-and these insignificant animals are the analogues of those forms in which we have reason to believe sensitive life first appeared in our world. "From this origin of organic life, there is no break in the chain of organic development, till we reach the existing order of things; no one Geological period, long or short-no one series of stratified rocks is every where devoid of traces of life. The world once inhabited has apparently never, for any ascertainable period, been totally despoiled of its living wonders. But these have many changes in the individual forms; great alterations in the generic assemblages; entire revolutions in the relative number and development of the several classes. Thus the systems of life have been varied from time to time, to suit the altered condition of the planet, but never extinguished. The earth, once freed from its early inadequacy to support life, according to the appointed laws, has since been prolific of vegetable and animal existence." It will be observed, that, contrary to what we might have naturally anticipated, animals seem to have preceded plants in the occupation of the globe, for no vegetable remains have been discovered in the older fossiliferous rocks. But we are not positively certain that this was the case, for though the mollusca in the Cambrian strata might prey upon each other, there is some antecedent probability in favour of marine plants co-existing with marine shell-fish; and it is perfectly possible to conceive, that in the metamorphic change which the slate rocks have undergone from the protrusion of igneous masses, all remains and traces of vegetable fibre have been obliterated.

CHAPTER IV.

THE SILURIAN SYSTEM.

NDER this title a great scheme of deposits is classed, lying upon the sloping sides of the slates of Wales, formerly included in the ill-defined grauwacke group, and constituting the middle division of that series. By the careful researches of Mr. Murchison these rocks have been firmly established as an independent system, having distinct physical features, lithological structure, and organic remains. The name is derived from the native denomination of the British region, where the system is developed in remarkable perfection. In the country of the Silures, that brave and warlike tribe maintained a desperate and frequently successful opposition to the military ambition of Rome; and ever after the defeat and captivity of their leader, the heroic and unfortunate Caradoc, the Caractacus of history, whose unbroken spirit and noble demeanour in adversity commanded the admiration of the Emperor Claudius, they rallied again to conquer, and were not finally vanquished until the reign of Vespasian.

The Bone Well, Ludlow.

"In ancient days,

The Roman legions, and great Cæsar found

Our fathers no mean foes."

Their territory embraced a considerable portion of South Wales, with parts of the border counties of England, though its exact limits cannot now be defined. It had within its bounds the counties of Radnor, Brecon, Hereford, and Monmouth, and probably ex