more pregnant with controversy.' (P. 1.)-'Stratum is a literal 'translation of the word bed, and most writers use one or other of 'these expressions indifferently. Professor Jameson, not con'sidering how injudicious it is to employ synonymes for the pur'pose of expressing contrast, has introduced a distinction between them. Similar contiguous masses are by him denominated strata, 'dissimilar ones beds. Mr. Martin has protested against this inno'vation, and few authors without the Wernerian pale appear dis'posed to adopt it. Those who feel the value of such a distinction 'would do well therefore to select some happier phrase to express 'it.' (P. 9.)

It has been supposed, without sufficient evidence, that stratification necessarily implies a formation by aqueous deposition, in the manner in which mud or sand is spread at the bottom of lakes or on the shores of the ocean: but volcanic rocks are sometimes regularly stratified: not only those which have been formed by showers of dust and scoriæ, but those which have flowed as melted lava. The tendency to split into parallel layers appears frequently to result from an imperfect kind of crystallization in the mass, and takes place in various rocks, particularly when exposed to atmospheric influence. The geologists who have been attached to the aqueous theory have denominated these parallel layers strata: but those who have adopted the Plutonian theory have refused to admit the stratification of such rocks. According to Mr. Greenough, this contrariety of opinion is caused by the indefinite application of the word stratum: 'every one uses the word, but no one 'inquires its meaning: the remedy is obvious, definition.'—As the remedy for this evil appears so obvious to the President of the Geological Society, we entertained the hope that he would have rescued the science from farther confusion and obscurity on this important subject, by giving his own definition of stratification: but we sought for such a definition in vain. Indeed, from the summary at the conclusion, we are rather led to infer that the word stratification is destitute of any precise meaning, and is utterly undefinable. ***

The continental geologists say that Mr. Greenough has quoted indiscriminately foreign writers of very unequal merit; and that he has given the opinions of authors who wrote early in the last century, when little was known of geology, as possessing the same value as the observations of the most accurate of modern geologists. We confess that there is much truth in this remark, which we have frequently heard on the Continent when Mr. G.'s book has been the subject of conversation; and the President himself, who indulges so often in a smile at the contradiction or supposed ignorance of preceding writers, will not be surprised to find that his brethren on the other side of the water are also disposed to en

courage les sourirs un peu malins when his own errors are discovered and criticised. They are wrong, however, in the inference "ex capite corporem," as applied to the President of an English Society

In Essay the third, Mr. G. seems disposed to admit that, previously to the great deluge mentioned in the second Essay, a deluge similar in kind had occurred, though perhaps not equal in extent to that which determined the present outline of the earth. He founds this opinion on the almost universal occurrence of conglo'merate and gray-wacke on the confines of what are called primi'tive rocks.' It may, however, be fairly asked how this conglomerate escaped being swept away by the second deluge? To volcanoes and earthquakes, Mr. G. seems disposed to allow a very limited range of action.-He states that it is not probable that the deluge was effected by a cause residing within the earth:for, he says, we are not aware of any force depending on 'the internal constitution of the earth, that could effect so 'great a revolution as the deluge:'-but are we to deny that the earthquake which destroyed Lisbon, in the middle of the last century, was produced by a force residing within the earth? That earthquake shook at the same time all Europe, a great part if not the whole of Africa, the continent of North America, and the West-India islands, and produced a violent agitation of the whole Atlantic Ocean. We say, then, are we to deny that this vast commotion of the surface of the globe was produced by a force residing within it, because we are not aware of any force depending on the internal constitution of our planet which could produce so mighty an effect? As well might we deny the emission of light from the sun, because we are not aware of any force in the internal constitution of that orb which can propel the particles of light with such astonishing velocity. On this subject, the Plutonist has greatly the advantage of the cometist; for he refers to a cause which, though he cannot explain it, is known to exist, and to be constantly operative: he can appeal to the evidence of his senses and of history, to show that many hundreds and even thousands of square miles of the earth's surface have been overwhelmed or disturbed by the same cause.

On Formations. By this term, the author observes, is 'meant a 'series of rocks supposed to have been formed in the same manner and at the same period. The idea is therefore purely theoretical.' It has been asserted by Werner that the greater number of rocks are universal formations; or, in other words, that each different order, as granite, gneiss, mica-slate, &c. is spread universally over the earth's surface, like the coat of an onion, and that the same rocks in distant regions were cotemporaneous. These positions, Mr. G., in common with many modern geologists, is disposed to VOL. I.

6

controvert; and his reasoning on this subject is satisfactory, and enriched with various illustrative facts.

'Enough has been said to make it evident, that neither any single stratum, nor single rock, nor any imaginable series of rocks can be traced in a continuous line round the globe. Similar strata, 'similar rocks, similar series of rocks are, however, found in different countries and in different hemispheres.-But will this similar'ity of character entitle us to suppose that they were once connect'ed? products of the same æra? precipitates or deposits from the 'same solvent? Certainly not; for similar rocks are continually seen 'in very different formations. How often do we observe, in a moun'tainous district, recurring strata composed of the same substance, 'separated by a vast thickness of strata composed of other sub" stances!' &c.

'As far as our present experience reaches, granite and gneiss seem to belong, peculiarly, though not exclusively, to the more 'ancient rocks: chalk, clay, sand, marle, loam, and rock-salt, to 'the more modern. Gray-wacke, sand-stone, clay-slate, quartz'rock, sienite, porphyry, green stone, basalt, serpentine, compact 'feldspar, seem common to both. In general, the younger rocks 'exhibit more abraded fragments than the others, more bituminous 'and saline matter, more organic remains.'

We agree with the author in his opinion respecting fossil organic remains, that, though they may serve to identify strata in a limited district, it is unreasonable to suppose that, if any stratum had ever extended over a large portion of the globe, it would contain the same animals in northern as in southern latitudes. Mr. G. doubts the correctness of many opinions that have been advanced respecting organic remains; and he denies that Zoophytes are the first 'born of animals; for the genealogy of the Nautilus is quite as 'long as that of the Madreporean polypus.' We apprehend, however, that most of those, who have advanced the opinion of the antiquity of Zoophytes, have admitted that many species of Zoophytes and shell-fish were cotemporaneous. We believe it would be difficult to prove that the remains of any vertebrated animals, and particularly of any that were viviparous, ever occur in the secondary strata below the mountain-lime-stone; and we deem the position still correct, that a regular gradation of animals from the more imperfect to the more perfect forms may be traced by their remains, as we ascend from the lower to the uppermost strata: which opinion we do not conceive to be invalidated by any statement that the present author has advanced. The subsequent observations on what are called the Fresh-water-formations are particularly deserving of attention.

'The alternation and occasional intermixture of sea-shells with 'those of fresh water, is common to all the secondary strata, and

'not unknown in the transition. The gray-wacke slate of the 'Harz contains encrini and reeds. Sea-shells, accompanied by 'impressions of fern, are observable in the dunstone of Ludlow and 'South Wales. Coal-shales and nodules of iron-stone, exhibiting 'casts of fresh-water muscles, are often interposed between the co'ralline lime-stones of the northern counties. The monitor, which 'occurs in the copper-slate of Thuringia, is associated with fresh'water fishes and marine shells. The lias affords ferns, nautili, 'and crocodiles; the slate of Stonesfield, remains of birds, beasts, 'and marine animals. The Petworth and Purbeck marbles, con'taining a species of paludina, alternate with beds of sand-stone, 'charged with marine univalves and bivalves; fruit and leaves are 'found with marine exuviæ in chalk. The clay at Sheppy Island, 'abounding in sea-shells, is reported to yield no less than five hun'dred varieties of fossil fruit; fresh-water shells intermixed with 'marine have been observed, also, at Barton Cliff, at Brentford, 'and other spots near London, in the same bed. The alternation ' of fresh and salt-water productions at Headen in the Isle of Wight, ' and in the corresponding strata of the basin of Paris, is notorious. 'At Guespelle, at Pierre-Laie, at Grignon, &c. sea-shells are in'termixed with fluviatile. At Montmartre the gypsum exhibits 'animals of land, air, and water; the middle beds of that rock con'tain fresh-water shells; the upper and lower, marine.

'How these extraordinary alternations and intermixtures are to 'be accounted for, and whether they are attributable, in all cases, 'to one and the same cause, it is difficult even to conjecture.

'It should be recollected that many of the opinions here com'bated were advanced at a period when much less was known than 'is known at present, and would now perhaps, if opportunity offer'ed, be disclaimed even by their authors. I make this observation 'not in candour merely, but in prudence; being satisfied that if 'geological science continues to advance at the rate it has done 'lately, the Essays now submitted to the public will, before many 'years have elapsed, be found to contain as many errors as they 'presume to correct.' Yet we can scarcely perceive any necessity for this apology; since the opinions which the author has advanced as his own are so few and so cautiously guarded, that he can never be convicted of many errors, unless we should call error the constant opposition to every theory that has been advanced by preceding writers. A former president of the Geological Society has well observed that the determination to oppose all system was itself a system, and like other systems had a tendency to obstruct the candid admission of facts and arguments. We entertain much respect for the character and talents of the present author, than whom few persons have had a more extended range of survey, or are better qualified to advance the science of geology by their own ob

servations; and we would beg leave to suggest that one page of accurate observations is worth a whole volume of doubts. With these feelings, we cannot but regret that Mr. Greenough, who now presides over the Geological Society, has so rarely contributed to the volumes which have been published by that body; and the rather because we know not any observer, either in this country or on the Continent, who could more amply enlarge our stock of geological facts, if the dread of falling into errors did not prevent their publication.

[From the Edinburgh Review.—Jan. 1820.]

On the same Work.

We are partial, perhaps, to this book, from its hostility to that geological dogmatism with which we have been so often offended, and its patronage of that wholesome skepticism to which we have always been so much inclined; and yet, if it had fallen in less happily with our own opinions, we think we should have had the candour to say, that we had never before met with such a treasure of information, and so much bold and free reasoning, in so small a volume, and on such a subject. We have no time at present, to grapple with the author's arguments; and it is extremely difficult to give any continuous abstract, or analysis of statements already so compactly arrayed. But we must endeavour to give our readers some notion of their general tenor, and shall touch on some of the more prominent features of each Essay-referring to the work itself for a great variety of important particulars, and especially for a rich display of illustrations and examples.

ESSAY I. On Stratification.-From a great collection of contradictory passages in the writings of eminent geologists, Mr. G. proves, not only that the stratification of granite, and some other rocks, is a point not yet ascertained; but that some of the main principles connected with the doctrine of stratification in general, are by no means satisfactorily established. Thus, although the parallel planes exhibited by the surfaces of different beds, may frequently have been effected by alternate suspensions and renewals of depositions, yet the same phenomenon is often produced by other causes; as in basaltic pillars, in backs and cutters, in the laminæ of crystals, &c. Besides, the greater or less frequency of the recurrence of parallel planes, depends on the nature of the substances deposited,-granite, porphyry, serpentine trap, salt and chalk, presenting themselves in thick masses, argillite in