by examples (which teach better than general descriptions) a view of the present condition of the art in the metropolis, as compared with the past. Upon the whole, it will be seen that we have reason to congratulate ourselves upon the progress we have made. Eccentricities, like the Panopticon, continue to be tolerated -a portion of our recent public edifices fall short of what we had reason to expect-certain domestic houses, such as those in Belgrave and Eaton Squares, exhibit no symptoms of reviving taste; but, on the other hand, the majority of our new streets display a marked improvement-some of our cotemporary public buildings are noble structures-and the two latest mansions upon a palatial scale surpass anything which previously existed. But there is no security that we shall continue to advance, or shall even keep what we have gained, unless the public can control by their judgment the caprices of individuals. It is for the gratification of the many, and for the sake of their commendation, that beauty is studied, and until they can distinguish between what is good and what is bad, architects labour in vain. In the hands of some the profession will be turned from an art into a money-making business; others, whose ability is not equal to their ambition, will be employed in preference to better men, and the Wrens and the Barrys will be fortunate if, besides being deprived of the stimulus of praise, their plans are not marred by the want of knowledge in their patrons of the common principles of design.

ART. IV. Siluria. The History of the oldest known Rocks containing Organic Remains. By Sir Roderick Impey Murchison, G.C. St. S., D.C.L., M.A., F.R.S., &c. London. 1854.

WE

E are seated comfortably in our new house at the Westend of London. We have chosen the site of our residence with care, selecting a spot where the foundation should be gravel and not clay. Naturally of an inquisitive disposition, we have not stopped short at the knowledge of the simple fact, but have sought to know what this gravel' and 'clay,' about which we hear so much in London conversation, may be. A geological friend tells us that they are the elephant gravel' and the 'London clay,' and that the latter is infinitely older than the former. As elephants have not, during historical times, been in the habit of scattering their tusks and bones over British fields, but have confined their peregrinations to the limited bounds of Astley's, Wombwell's, and the Zoological Gardens, we feel quite sure that the gravel in question was accumulated a very long time ago. As to the clay, Highgate-hill, our friend tells us,

is made of it; and he says that in some places about London it is 600 feet thick. Underneath it is chalk, and to get a good supply of water we must bore through chalk as well as clay. We are advised to read Prestwich On the Water-bearing Strata around London,' and to look at Milne's 'Sections of London Strata,' and then we shall understand the matter better. Having shares in water companies, and being tired of American novels, we determine to take the advice of our friend, and seek a new pleasure by reading up geology,-just so much of it, at least, as is quite certain. The good Rector of our parish in the country, a very worthy man and excellent scholar, has told us that there is some truth in the practical part of the science, but that its theories are all doubtful, and no two geologists can agree about them. There are other reasons why we should know something of the subject, having been tempted to take shares in coal-mines at an unpronounceable locality in North Wales, which certainly seems to be singularly uncarboniferous, and to require a great deal of money from the shareholders in order to get at the coal. We subscribe to the Miners' Adviser'-a weekly paper of high repute in the speculative world—and read all the correspondence, the gist of which is to the effect that every mining enterprise at present in progress is sure to be productive, and that geology is all rubbish.' Our manager at the coal-mines also takes in the 'Miners' Adviser,' and assures us that he agrees in everything that its correspondents write, being satisfied, after long experience, that there is nothing like practical knowledge. He does not, however, despise geology, though he says the so-called geologists are very ignorant. He has a prophet of his own, whom he calls Evan Hopkins, a philosopher who he says must not be confounded with a famous geologist and great mathematician at Cambridge known as William Hopkins. He talks fluently and well on these matters, and uses many excellent technical terms. Several friends in the City think highly of our manager's judgment, and are quite ready to follow his advice about investing money in mining-shares. Our geological friend, however, seems to entertain opinions different from those of our practical manager, and holds the authority of the latter gentleman in small account. He demands to know precisely where the coal-mines are, pulls a parti-coloured map out of his pocket, looks at it attentively, and shakes his head. He is more cautious than our manager, and, though evidently desponding, does not venture upon a definite opinion before the maps of the geological survey are procured. These maps are new to us; but a glance suggests that we ought to have asked for them before, and that, if the state does the people a benefit by putting accurate information within their

reach,

reach, for their own sakes they should take advantage of it. Our friend explains to us the colours of the map, and communicates the intelligence that our imaginary coal-mines are in the Llandeilo flags or Wenlock shales, we forget which. Either, however, according to the geologist, was quite sufficient, and the sooner we get rid of our manager and break up the works the better for our purse. Our friend is evidently too sure of what he is saying to permit of a doubt; and we begin to see daylight in geology.

Disappointment speedily gives way to curiosity. New questions suggest themselves. How old are the said flags and shales, and how much older than the clays and gravels of London? Having grown geologically wiser since our speculation in the Llanffandidl coal-mines, we are now in a condition to afford some information on these points, and to speak not without authority upon geological questions generally.

The flags' and 'shales,' called Llandeilos and Wenlocks, are Silurian rocks; the former part of the Lower, the latter of the Upper Silurians. Between the newest of the Silurian strata and the London clay there is a prodigious geological interval and a vast thickness of rock formations of various kinds. Were we to bore through the clay in London, we should in all probability have to sink through many thousand feet of ancient consolidated sediments before arriving at the Silurians. Let those of our readers to whom geology seems a mystery go down to some place upon the sea-coast, where the various beds of clay and rock are seen resting upon each other in succession, and in consequence of violent movements that have agitated the earth's crust, are so inclined or set on end that their order is as manifest as in a drawing or plan. There are many such places. On the shores of the Isle of Wight, for example, the London clay itself, with its peculiar fossils, may be seen upheaved and resting on the chalk, under which are various sands and clays, some of marine, some of fresh-water origin, as may be inferred from the organic remains they contain, all belonging to what is termed the cretaceous system. In none of these strata are found fragments of animals or plants identical with any now living in the world. All they contain, moreover, are different from those entombed in the great series of oolitic rocks that lies below the cretaceous; and these again, in turn, from the contents of the far more ancient Upper Palæozoic strata, to which group of great formations belong, among others, the coal-bearing beds of our country. Between these last and the Silurians are, in Britain, several thousand feet of distinct rock-formations, called Devonian, and to which the well-known old red sandstone belongs. The lowest of the Devonians rests on the uppermost of the Silurians.

This order of succession, thus briefly indicated, is found to be constant all over the globe wherever the hammer of geologists has been wielded by competent observers. Not that all the members of the complete roll of formations are universally diffused and invariably present; on the contrary, it is not likely, or indeed possible, that in any one place there can be met with the whole series of strata. But when one locality is compared with another, and section tested by section, the order of relative sequence proves fixed and invariable. Occasionally, though rarely, the explorer may be momentarily deceived by some convulsive overturn or excessive crumpling and rolling of the beds; but a brief search and tracing out of the rocks soon brings the exception within compass of the rule. The scale or index of order of sedimentary formations varies only in its wording in different geological treatises on the actual sequence all are agreed.

The entire assemblage of rock-formations just alluded to contain organic remains; so do the Silurians that lie below them. But not very many years ago the strata beneath the old red sandstone were regarded as presenting little better than a geological chaos. They were mentioned as 'grauwacke,' a good old vague German word that served to conceal ignorance. The ablest geologists regarded them with a sort of respectful despair, and treated them as antiquities of whose history no clue could be obtained. No one surmised that they contained as excellent and abundant proofs of life and order as any of the superincumbent strata. To make this discovery, to work it out in all its details, to establish a classification of these primeval strata which should enable geologists throughout the world to interpret their equivalents, were the worthy and admirable tasks reserved for and performed by the author of the Silurian system, who now, twenty-three years since he commenced his work on the banks of the Wye, directed thither by the sagacity of Dean Buckland, gives to the world with just pride a retrospect of his researches and a record of the results to which they have given origin, and the proofs those results have afforded of the truth of his generalizations. More remarkable or more important service has not been rendered to practical geology since the organization of the science than that which it owes to Sir Roderick Murchison. In itself this result would be a full claim, for fame. The author of Siluria' has, however, gathered other and equally honourable scientific laurels, and his geological researches have extended, with equal success, over almost the whole range of the greater rock formations.

Thirty thousand feet of strata, or more, including in the reckoning beds of contemporaneous igneous rocks, have been ascertained to belong to the great Silurian series in Wales alone, or on

the

the borders of that province. This enormous accumulation may give some notion of the importance of Silurian rocks. A large, probably the larger, part of this mass seems to have been formed in the depths of primæval oceans. The vast duration of time required for the aggregation of so much sedimentary matter as goes to its constitution must be estimated not merely by the amount of these series, but chiefly by the changes that were taking place in the population of the Silurian seas. The four chief subdivisions of the Silurians, in the original classification of their explorer, viz. Ludlow, Wenlock, Caradoc, and Llandeilo- the two former constituting his Upper,' and the two latter his 'Lower Silurians'-are all and severally characterised by peculiar assemblages of organic remains. Yet are they all linked together by these very fossils, either by the general aspect of the fauna originating in the peculiarities of its generic elements, or by the presence of species that are common to several subdivisions. Excluding the fossils of the Upper Caradoc, about which there is a difference of opinion as to whether it should be classed with the Upper or the Lower Silurian, there are known to be nearly one hundred species of organic remains common to the two great sections of the Silurian system as presented in the British Islands. On data such as these Sir Roderick Murchison founds his opinion that the Silurian is an unique system; and since no comparable assemblage of ancient beings can be discovered in the rocks that lie at its base, he maintains that the Silurian fauna was not merely primæval, but protozoic, and that in the centres of the Silurian rocks we have presented to us the evuences of the earliest forms of life which inhabited the surface of our planet. An interest, sui generis, consequently belongs to the Silurian system and to the investigation of the arrangement and structure of the world's foundation stones to which it claims to belong. Yet the oldest fossiliferous Silurians rest on unfossiliferous rocks of sedimentary origin, and consequently, through their pre-eminent antiquity, are deserving of searching inquiry, for in them, if anywhere, we may hope to find evidences of the world's beginning.

The geological map of England exhibits, on the Welsh border, a small patch of peculiar strata in the neighbourhood of Shrewsbury, to be matched only by a similar and somewhat larger district at the north end of Cardigan Bay, the country where Harlech and Barmouth are situated. There are few spots more interesting on earth to the geologist than those sterile and inconspicuous tracts. To the first we would especially call attention. It constitutes the hilly region of the Longmynd of Shropshire, and is the oldest morsel of Old England. The Longmynd scarcely deserves

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