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blistered all over as it were with little minor excrescences here and there, many concealed and buried under more recent eruptions; and the whole penetrated in various directions by veins or walls of rock more or less nearly upright.

was...

As molten rock does in many instances succeed in forcing its way to the surface either on dry land or at the bottom of seas and lakes, we should naturally expect that there might be also many cases in which it did not so succeed, but lay buried still in the interior of the earth, and after a time cooled where it Moreover, as the lava-stream of a volcano is merely the boiling over of a vast quantity of melted stone deep below ground, and the part reaching the surface must be a small portion of the whole mass, it must happen sometimes that a great portion of the remainder of the molten rock will cool down ultimately in the interior of the volcano, and perhaps pretty low down under a great pressure of other rock, and much more slowly than the actual lava... It might be naturally anticipated that the rocks, when thus cooled down, slowly and under great pressure, and perhaps without the access of either air or water, would exhibit somewhat a different structure from the volcanic rocks.

Whenever we examine rocks, therefore, that had once been deep-seated, but which are now exposed to our observation, we should expect to find here and there some that, though of truly igneous origin, yet were not exactly similar either in structure or perhaps in composition to those which we find on the surface of volcanoes. As a matter of fact we do find such rocks, which we know to be igneous ones for the following reasons:

First, some of them do resemble, in structure and other characters, some of those which we know to be products of volca

noes.

Secondly, when we find them in connection with aqueous rocks, we perceive that they are not regularly interstratified with them, but often intrude irregularly among them, sometimes in vertical walls cutting through them, sometimes in rude shapeless masses, sometimes in fine branching veins, running for many yards through the aqueous rocks, splitting up into narrow strings, and twisting in various directions... This takes place in such a way that it is plain the aqueous rocks were in such places first formed, and have then been disturbed, broken, and cracked in various directions, the cracks being filled up by the intrusion or injection of the other rock in a fluid state.

Thirdly, it is shown that this fluidity was the result of great

heat, in fact a molten fluidity, because the aqueous rocks near the injected masses have evidently undergone such an alteration as is the effect of heat; that alteration being greatest closest to the intrusive rock, and dying away as we recede from it... For instance, we find soft sandstones hardened or half fused into quartz rock; shales baked into jasper or Lydian stone, or into a substance resembling porcelain; chalk altered into crystalline marble, coal converted into cinder, or into a substance resembling coke.

Rocks that have the characters of these intrusive masses, dykes or veins, must be igneous rocks, and such are the rocks called basalt, greenstone, feldspathic, trap, syenite, and granite.

As the aqueous rocks are all stratified more or less completely, and often go by that designation, so these rocks, never having any true stratification however they may sometimes assume its appearance, are often called unstratified rocks. In order to distinguish them from volcanic rocks, the terms hypogene and Plutonic have been applied to them, both indicating that they have been formed or brought into their present state below ground, while volcanic rocks have always been ejected above the surface of the earth, whether that surface were there covered with water or only with air. J. Beete Jukes.

CARBONIFEROUS GROUP: COAL.

COAL occupies an important place in that series of sedimentary rocks which contains the records of ancient life; therefore termed the paleozoic period. This series, with a partial interruption of the oolite at Derby, extends from Stonehaven in Scotland, to Milford in South Wales; and the coal has thrust aside other naturally overlying rocks, at various points on this central range... Chiefly on both sides of the Forth, and of the Tyne, in Lancashire, and the West Riding, Stafford, and Warwick, Bristol, and South Wales... Coal is of vegetable origin, and an imaginative picture of the probable process of its formation is thus drawn by the late Hugh Miller:

"Imagine to yourselves a low shore, thickly covered with vegetation. Huge trees of wonderful form stand out far into the water. There seems no intervening beach. A thick hedge of reeds, tall as the masts of pinnaces, runs along the deeper bays, like water-flags at the edge of a lake... A river of vast

volume comes rolling from the interior, darkening the water for leagues with its slime and mud, and bearing with it to the open sea, reeds, and fern, and cones of the pine, and immense floats of leaves, and now and then some bulky tree, undermined and uprooted by the current. We near the coast, and now enter the opening of the stream. A scarce penetrable phalanx of reeds, that attain to the height and well nigh the bulk of forest trees, is ranged on either hand... The bright and glossy stems seem fluted like Gothic columns, the pointed leaves stand out green at every joint, tier above tier, each tier resembling a coronal wreath, or an ancient crown, with the rays turned outwards, and we see a-top what may be either large spikes or catkins... What strange forms of vegetable life appear in the forest behind! Can that be a club-moss that raises its slender height for more than fifty feet from the soil ? Or can these tall, palm-like trees be actually ferns, and these spreading branches mere fronds? And then these gigantic reeds! are they not mere varieties of the common horsetail of our bogs and morasses, magnified some sixty or a hundred times?... Have we arrived at some such country as the continent visited by Gulliver, in which he found thickets of weeds and grass tall as woods of twenty years' growth, and lost himself amid a forest of corn fifty feet in height. The lesser vegetation of our country, its reeds, mosses, and ferns, seem here as if viewed through a microscope: the dwarfs have sprung up into giants, and yet there appears to be no proportional increase in size among what are unequivocally its trees Yonder is a group of what seem to be pines,-tall and bulky, 'tis true, but neither taller nor bulkier than the pines of Norway and America, and the club-moss behind shoots up its green hairy arms, loaded with what seem catkins, above their topmast cones. But what monster of the vegetable world comes floating down the stream, now circling round in the eddies, now dancing on the ripple, now shooting down the rapid? It resembles a gigantic star-fish, or an immense coach wheel, divested of the rim... There is a green dome-like mass in the centre, that corresponds to the nave of the wheel or the body of the star-fish ; and the boughs shoot out horizontally on every side, like spokes from the nave, or rays from the central body. The diameter considerably exceeds forty feet; the branches, originally of a deep green, are assuming the golden tinge of decay, the cylindrical and hollow leaves stand out thick on every side, like prickles of the wild rose on the red, fleshy, lance-like shoots of a year's growth, that will be covered two seasons hence with

...

flowers and fruit... That strangely formed organism presents no existing type among all the numerous families of the vegetable kingdom.

"There is an amazing luxuriance of growth all around us. Scarce can the current make way through the thickets of aquatic plants that rise thick from the muddy bottom; and though the sunshine falls bright on the upper boughs of the tangled forest beyond, not a ray penetrates the more than twilight gloom that broods over the marshy platform below... The rank steam of decaying vegetation forms a thick blue haze, that partially obscures the underwood. Deadly lakes of carbonic acid gas have accumulated in the hollows; there is a silence all around, uninterrupted save by the sudden splash of some reptile fish, that has risen to the surface in pursuit of its prey; or when a sudden breeze stirs the hot air, and shakes the fronds of the giant ferns, or the catkins of the reeds... The wide continent before us is a continent devoid of animal life, save that its pools and rivers abound in fish and mollusca, and that millions and tens of millions of the infusory tribes swarm in the bogs and marshes.”

GEOLOGICAL ASPECT OF ENGLAND.

THE region of Central England was once a broad ocean sound, that ran nearly parallel to St. George's Channel; there rose land on both sides of it; Wales had got its head above water; so had the Cotteswold hills in Gloucestershire... The waves beat against the Malverns on the one side and the Cotteswold hills on the other; they rose high along the flanks of the Welkin; the secluded dells of Hagley were but the recesses of a submarine rock shaggy with sea-weed, that occupied its central tide-way; while the Severn, exclusively a river of Wales in those days, emptied its waters into the sea at the Breidden hills in Montgomeryshire, a full hundred miles from where it now falls into the Bristol Channel... Along this broad sound, every spring when the northern ice began to break up - - for its era was that of the British glacier and iceberg huge ice-floes came drifting in shoals from the Scottish coast, loaded underneath with the granitic blocks, which they had enveloped when forming in firths and estuaries; and as they floated along, the loosened boulders dropped on the sea-bottom beneath. Here lie scores in the comparatively still water, and there lie hundreds where the conflicting tides dashed fierce and strong...

In the tract extending from the hamlet of Trescot to the village of Trysull in the south-western parts of Staffordshire, the quantity, of occasionally gigantic dimensions, of these northern boulders, several tons in weight, may well excite surprise, seeing that they there occupy one of the most central districts of England... Here the farmer is incessantly laboring to clear the soil, either by burying them, or by piling them up into walls or hedge-banks; and his toil, like that of Sisyphus, seems interminable, for in many spots new crops of them, as it were, appear as fast as the surface is relieved from its sterilising burden... So great indeed is their abundance, that an observer unacquainted with the region would feel persuaded he was approaching the foot of some vast gigantic range, and yet the source of their origin is one hundred and fifty miles distant... The softer formation of the country we find represented, like the shale-beds on the shore, by wide flat valleys or extensive plains; the harder by chains of hills of greater or lesser altitude, according to the degree of solidity possessed by the composing materials... A few insulated districts of country, such as part of North Wales, Westmoreland and Cornwall, where the Plutonic agencies have been active, we find coming under the more complex law of Scottish landscape; but in all the rest, soft or hard, solid or incoherent, determines the question of high or low, bold or tame... Here, for instance, is a common map of England, on which the eminences are marked, but not the geologic formation. These, however, we may almost trace by the chain of hills, or from the want of them... The hilly region, for instance, which extends from the lowlands of Scotland to Derby, represents the millstone grit and mountain limestone, solid deposits of indurated sandstone and crystalline lime, that stand up amid the landscape, like the harder strata on the wave-worn sea coast... On both sides of this mountainous tract there are level plains of vast extent, that begin to form on the one side near Newcastle, and at Lancaster on the other, and which, uniting at Wiskworth, sweep on to the Bristol Channel in the diagonal line of the English formations... These level plains represent the yielding semi-coherent new red sandstone of England. The denuding agents have worn it down in the way we find the soft shale-beds worn down on the sea shore... On the west we see it flanked by the old red sandstone and Silurian systems of Wales and western England — formations solid enough to form a hilly country; and on the east by a long hilly range that, with little interruption, traverses England diagonally from Whitby to Lyme Regis... This elevated line is the oolitic

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