islands, the coal of other formations either has been or is being worked. Tertiary lignites were worked at Bovey in Devonshire; and coal-fields in the Secondary rocks are to this day worked, as, for example, in the oolite of Brora in Sutherland, and Whitby in Yorkshire. With us, it is true, such seams are not very extensive, either as to area or vertical thickness. In the New World, however, things are very different. The Richmond coal-field, in Virginia, belongs to the Secondary period, and even surpasses, in richness and thiekness of seams, the true coal measures of the British and Old World basins. One of the seams in this coal-field is in some places from thirty to forty feet thick, and composed of pure bituminous coal, which, Sir C. Lyell tells us, "When analysed, yields the same proportions of carbon and hydrogen as the Newcastle coal; a fact worthy of notice, when we consider that this fuel has been derived from an assemblage of plants very distinct specifically, and in part generically, from those which have contributed to the formation of the ancient or Palæozoic coal."* Still, important though these later coal formations may be, it cannot be denied that the great coal-fields of the world, both old and new, belong to the Palæozoic rocks; and certain it is, whatever may be the reason, that "these Palæozoic coal-fields are more regular, more uniform over large areas, and in that sense more to be depended on, than those of newer date." Below the coal measures proper, the fossilized vegetable remains are scanty. With the exception of some insignificant bands in Canada, the Old Red Sandstone is altogether barren of coal, though vegetable fragments occur in its shales and flagstones. In the still older rocks, Silurian, Cambrian, and Laurentian, where metamorphism has been largely at work, we find thin bands of anthracite and graphite (black lead). In these, however, the mineralization has been so perfect, and all traces of vegetable structure have been so effectually obliterated, that it is impossible even to speculate as to their marine or terrestrial origin, or even in all cases to be perfectly sure that it ever was a vegetable organism at all. The probability is that it is of vegetable origin, and that in it we have simply the most thoroughly mineralized form in which we find masses of vegetable débris, just as in the peat-moss we find it in its least compact and least altered form; for, to quote from Mr. Page,— "The truth is, coal occurs in the earth's crust in every stage of development; from the peat-mosses and swamp-growths still in process of accumulation on the surface, down through the Tertiary brown coals to the bituminous stone coals of the Secondary and Primary periods, and from these again down to the still older non-bituminous anthracites and graphites. All, in fact, have had a similar origin. They are mere vegetable masses that have undergone different degrees of mineralization, the recent vege * "Manual of Elementary Geology" (1855), p. 332. impress alike on almost every mountain-side world we live in. This universal prevalence duced by the great ice epoch is very rema persons who go about with eyes who have not gorges of all our British Alpine and sub-A observant tourist has seen it for himself, in (indicated by Dean Buckland) at Pont Aber of Benglog, at the head of Nant Frangon. remarked to us, "You geologists see things wit ours;" and, we may add, sometimes see thin There is some necessity for caution to be o every rounded, scored, and furrowed rock to 1 An incidental remark of Mr. Page's may sug such conclusions. In speaking of the part p altering the configuration of the country, he may seem, the drifting of sand over the surfa has been known to wear and polish down thei grind out grooves and furrows like those pro tinued motion of glacier ice, or the flow of 1 Such, we doubt not, is the history of the groo rounded granite surfaces which crop up from t intervenes between the base of Errigal and t near Gweedore, in County Donegal, though it 1 of glacial action: the fatal objection to a gla among other things, the wide extent of country ing and scoring may be traced. Reverting, however, to the true glacial epocl that there remains much to be done and obser tend to have arrived at any satisfactory con The polishing on more faces than one, and t directions than one, of small boulders imbedde this geological period, seem to furnish problem the common theory of glacial transportation o precisely such rounded, polished, doubly strat iferous limestone the writer has repeatedly dis boulder clay of the hills to the west of the city Mr. Page has done wisely in grouping togeth coal and coal formations, a full account of tho deposits which do not belong to the Carbonifer called. From the vast importance and develop boniferous rocks of Great Britain, as well as insignificance in our islands of other deposit among the later formations, the term Coal with restricted to the produce of the coal measure islands, the coal of other formations either has been or being "When analysel, yield the same peptions of carbon and bydren hich have received the name of the range of hills of some altitude,England, and attains a thickness e of it has undergone entire metaeen converted into serpentines (like ns in the west of Ireland), and its erated. But this serpentinous limely to revolutionize all our cherished anic life. We had long acquiesced all below the Cambrian was Azoic. selves were pronounced, at least in rmouth schists of North Wales, the the Longmynd or bottom rocks of of a fossil, and to be as destitute of mica-schist successions that underg beds, indeed, at Bray in Ireland, eal unmistakeable fossil, which was is but the other day that Sir R. everence upon this zoophyte; "for, ous researches, it is the only animal. w stage of unequivocal sedimentary spoken like a true philosopher; but e vicissitudes of fossils! The Oldminence; it adds one more to the e so-called Azoic rocks, of immeasurit, have yielded a fossil, well named ssil, for its organic nature has been vidence and the opinion of compeits favour,-it belongs to the very e of the foraminifera, those minute. scarcely describe them as flesh,licious or calcareous cells, pierced a, whence their name), and which Still, important though these later coal formations may be, it cannot The truth is, coal cars in the earth's crust in every stage of develop Mal of Elementary Geology" (1855), p. 892 naked eye when they are aggren that a large part of the chalk of f such lowly organisms: the same is t the bottom of the Atlantic: and work in these strata of primeval te that the usual measure of time ever to the mind. And who knows dat life"? the dawn of utionizing of all our foregone conce in the more recent deposits, the (1854), p. 32. table full of volatile matters, the lignites less so, the bituminous coals giving off smoke and flame, the anthracites barely smoking, and the graphites masses of pure debitumenized carbon.”—(P. 102). Geology, as we remarked in the outset, is of all the natural sciences that one which seems destined to undergo most reconsideration, if not reconstruction. From the very nature of the case this is an obvious necessity. Every year adds to the number of fresh observers who enter into the labours of the great giants who have pioneered for them, and extend, digest, verify, or correct their researches. The number of fresh hands at work is constantly increasing; but so also is the field of research. It is little short of astonishing that the geological classification in the main, as we study it at the present time, was elaborated from the investigation of so very limited a geographical area as the British Islands. It is astonishing that within so confined a circle there should have been such diversity of formation, so broken up and exposed as to furnish to the student of nature a complete system of geological succession, to which subsequent research in either continent has made but few additions or modifications of a really important nature. If we take the main body of the British geological formations, from the Cambrian to the Tertiaries, we shall find that—with the exception of the much greater development of the Permian system in Eastern Russia; with the addition of one wellmarked member, the Muschelkalk, to the so-called Trias; of the more amply developed Neocomian or Neuchâtel formation to our Greensand; of the nummulitic limestone to our Eocene Tertiaries, -geology is still pretty much what its English students have made it as the result of their observation of the rocks of our own islands. Changes of detail there have been, and constantly are plenty; but since the labours of Sedgwick and Murchison reduced to system and order the apparently hopeless confusion of greywacke and trap that forms the base of our geological system, and evoked out of this chaos the well-defined and clearly arranged Cambrian and Silurian groups, no change of importance has been adopted by geologists within the abovementioned limits. It is on the confines of this series, both upwards and downwards, that change of opinion has taken place most conspicuously, and it is on the upper frontier line of the series, that is to say, in the post-Tertiary - Quaternary, as it seems we now are to call it,-group that most remains to be done, and most uncertainties to be patiently cleared up. Beneath the base of the Cambrian group, underlying the lowest unfossiliferous Longmynd grits of Murchison, and apparently contemporaneous with the gneiss of the Scottish Grampians and Scandinavian Alps, there has been brought to light, by the labours of the Canadian Geological Survey, a series of highly crystalline strata in the valley of the St. Lawrence, which have received the name of the Laurentian System. It forms a range of hills of some altitude,mountains we should call them in England,-and attains a thickness of some 30,000 feet. The whole of it has undergone entire metamorphism; its limestones have been converted into serpentines (like those of the Connemara mountains in the west of Ireland), and its lines of stratification all but obliterated. But this serpentinous limestone has been destined apparently to revolutionize all our cherished beliefs as to the beginning of organic life. We had long acquiesced in the conviction that at least all below the Cambrian was Azoic. The very Cambrian rocks themselves were pronounced, at least in their lowest beds, such as the Barmouth schists of North Wales, the chlorite schists of Anglesea, and the Longmynd or bottom rocks of Shropshire, to yield not a trace of a fossil, and to be as destitute of organic life as the gneissic and mica-schist successions that underlie them. In the corresponding beds, indeed, at Bray in Ireland, there was found a zoophyte, a real unmistakeable fossil, which was christened Oldhamia. It seems but the other day that Sir R. Murchison bade us look with reverence upon this zoophyte; "for, notwithstanding the most assiduous researches, it is the only animal relic yet known in this very low stage of unequivocal sedimentary matter." Cautious words, and spoken like a true philosopher; but iù Врóτεiа πрáypara,-alas for the vicissitudes of fossils! The Oldhamia is deposed from its pre-eminence; it adds one more to the list of dethroned monarchs. The so-called Azoic rocks, of immeasurably greater antiquity even than it, have yielded a fossil, well named the Eózoön. If it really be a fossil,-for its organic nature has been called in question, though the evidence and the opinion of competent judges incline strongly in its favour,-it belongs to the very lowest forms of life. It is one of the foraminifera, those minute. specks of sarcode, for one can scarcely describe them as flesh,— which make themselves tiny silicious or calcareous cells, pierced with still tinier holes (foramina, whence their name), and which only become conspicuous to the naked eye when they are aggregated in masses. It is well known that a large part of the chalk of England consists of the exuviæ of such lowly organisms: the same is true of a deposit now forming at the bottom of the Atlantic: and here we find the same thing at work in these strata of primeval antiquity, an antiquity so remote that the usual measure of time. fails to convey any notion whatever to the mind. And who knows whether we have yet really arrived at "the dawn of life"? But after all, the greatest revolutionizing of all our foregone conclusions in geology has taken place in the more recent deposits, the "Siluria" (1854), p. 32. |