and omissions, and that the rocks which are described as primitive are frequently found mixed with those of the second order. His objections, in short, do not reach the great question of the igneous or aqueous origin of mineral bodies, but solely. respect certain minor points in the detail of classification.

ap.

"In reviewing," says he, "the history of the strata described in the ten preceding chapters it seems evident, to me at least, that their parently arbitrary intermixture and general character is such as to preclude the possibility of framing any rational hypothesis as to their origin: and certainly there is no natural process in existence, capable of producing any of the commonest phenomena by which they are particularly characterized. Where, for instance, do we now see the formation of granite, or syenite, or porphyry, &c.? where do we see the production of metallic veins, or of beds of rock salt, or even of genuine coal? On the truth of these positions I need not insist, since they are not likely to be disputed by even the most cursory observer: but as I may possibly be thought to have confounded the true arrangement of many of the strata above described, I beg leave to offer a few remarks on that. point.

"In the preceding chapters I have attempted to shew, that the frequent alternations and mutual transitions, observable in the strata below the rock marl, are such as effectually to prevent a distinct classification of them: and I believe that even the rock marl not only appears under the varying form of mere clay, and fine and coarse grained gritstone, but that it sometimes assumes the character of a more or less perfectly defined porphyry and amyg daloid; and even insensibly passes into any of the rocks from granite downwards, and alternates with many of them. But in saying this I do not mean to advance the indolent and unphilosophical proposition, that, because any rock may insensibly be traced into almost any other, (a fact however which those who have seen most will be most ready to allow,) there is therefore no difference between them: nor do I deny that this change of character appears to be connected with some law, which in a general point of view has assigned its place to each series of rocks: so that in a geographical distribution, allowance being made for partial devia tions, you pass from granite, mixed with hornblende rocks of va rious descriptions, upon that mixed class of slates and gritstones so very generally found contiguous to a granite district; and among the last mentioned you find interspersed the mountain lime and coal series; the whole being bounded by the rock marl formation, with its accompanying rock salt and gypsum. All that I maintain is this, that since the succession of the formations above the rock marl is usually to be traced with ease, and can be satisfactorily demonstrated to an indifferent spectator, the same succession in the formations below the rock marl ought also by analogy, if it exist, to be visible and demonstrable; and if not thus demonstra

ble,

ble, it is in some degree probable, that there is no such succession. But if in addition to this it can be shewn, which is I believe the case, that the rock marl can insensibly be traced into the state of mountain lime or schist, or gritstone; and that these latter can also insensibly be traced into granite, and syenite, and the various forms of hornblende rock; and, lastly, if all these rocks are found occasionally to alternate with each other, (and, if I am not misinformed, coal has been found under mountain lime, and mountain lime under even granite,) from all these facts I think it necessarily follows, that there is a connection between these rocks, which, if it does not justify us in classing them under one series, effectually prevents us from finding any fixed law of their suc cession.

"I am happy in being able to add the following powerful authorities in support of the opinion above expressed. Dr. Mac CulJoch, in speaking of the usual division of rocks into primary, transition, and flatz, is inclined to think that these are distinctions which are more easily made in the closet than in the field; and argues, that different strata which alternate must be collectively considered as of cotemporaneous formation *. Brogniart, in his account of the Cotentin, to which I have already referred, after having observed that granite and gneiss occur in a syenitic forma tion to the east of the Erzegebürge, and that this syenite overlies argillaceous schist, and even grauwacke; that Haussman and Von Buch found in Norway zoophytic limestone under a formation consisting of syenite, granite, porphyry, gritstone, and argillaceous schist; and lastly, that there seem to be very few granitic districts which can be referred to a primitive formation of granite, coneludes by saying, that at present there is a great difficulty in estab lishing a good division of the strata †.

"Saussure again observes, that the mountains of St. Bernard are a mixture of various strata, which have hitherto been ranged in different orders; but that the complete intermixture of these different orders, particularly of slates with quartz rocks, appears to perfect the proof of what he has often suggested, that philoso phers have been too hasty in classing different orders of mountains, and of establishing precise limits between primitive and secondary strata. It appears evident, he adds, that nature has not assumed those divisions for the rule of her operations; and that, if she has not made mountains of granite, strictly so called, incumbent on calcareous foundations, she has at least frequently mixed calcareous rocks and argillaceous schists with quartzose and micaceous schists and in closing his account of the rocks of Mont Blanc, he says, it cannot be too often repeated, that we may expect to find, and do actually find in the mineral kingdom, all kinds

"Geological Transactions, vol. ii. p. 410."

+ Cotentin, p. 25." "Saussure, tom. iv. p. 264, 265.”

of

of mixtures in all kinds of proportions: whence arises an infinity of mixed and indeterminate species *.", P. 130.

It will be readily acknowledged by every candid Wernerian, that there are exceptions to the regularity of succession in the strata of all the formations; that some members of the series are occasionally absent; that the component parts are combined in different proportions; and, above all, that there exist a thousand proofs of violence and convulsion. Before the waters had finally retired, they appear to have made considerable impression even upon some portions of the first formation; and it would seem that the precipitations also of the primitive substances themselves, were occasionally disturbed by the agitated state of the great solvent. The principal point however, which every geognost should labour to ascertain is, whether there are not formations of such distinct characters, and of such universal distribution, as prove that they must have proceeded from a general cause. Now, it cannot be denied that the primitive mountain-rocks of Werner are seen in every quarter of the globe, in Europe, in China, in Van Diemen's land, in Brazil, Mexico, and Canada, at the Cape of Good Hope, and in Bengal, occupying the same relative position, and composing the most elevated parts of the earth's surface. Granite, indeed, is not in every instance followed by gneiss, mica-slate, and clay-slate: there may be a gap in the succession occasioned by accidental causes, but the order is never reversed, and their geological relations are every where the same. Be it observed, however, that we speak of primitive granite, highly crystallized and destitute of all organic remains; for there is a granite of a newer formation, which is found connected with transitive rocks, and which perhaps may occasionally contain both shells and vegetables. It must not be concealed, notwithstanding all this, that it is, in many cases, extremely difficult, and in some cases totally impossible, to mark where the primitive rocks terminate, and the secondary commence; and this is a circumstance which the very conditions of the Wernerian theory would lead us to expect. The precipitations which formed the primitive rocks, be it remembered, are not represented as having been entirely stopped when the transition class was begun; it is merely said that the quantity of the particular matter of which the former is composed, felspar, quartz, and mica, had considerably diminished, and that the mechanical depositions were beginning to take place. The gray wacke of the transition formation is regarded by the Wernerians as the product of deposition, but

Saussure, tom. iv. p. 469."

the

the limestone, the greenstone, and indeed all the compounds of hornblende and felspar, in this order of rocks, differ from the primitive in no other circumstance than in not being quite so much crystallized, and in exhibiting a few organic fossils. Indeed, we should not be surprised to find a successive gradation from the oldest granite down to the newest floetz trap; and if it should be said in consequence of this that the nomenclature of the science ought to be changed, it would be conceded perhaps that better words might possibly be found out.

But really all this does not affect the ground-work of the Wernerian theory, and in fact goes very little further to invali date its leading doctrines than irregular verbs in grammar, or comets in the planetary system would go to prove that the grammarian and the astronomer are guided by no general rules. Professor Kidd holds the distinguishing tenet of the aqueous solution and consequent precipitation of the materials which form the crust of the earth; and when he maintains that the evidence in support of Werner's theory is imperfect, he alludes solely to his classification of the various rocky substances, and perhaps to the hypothetical assumption which is involved in the term transition. This we regard rather as an expression of the Professor's opinion that geognostic science is still in its infancy, than that the principles are erroneous upon which the disciples of Werner reason, and prosecute their researches. At least we will make bold to assert that his Geological Essay contains nothing inconsistent with the doctrines of that distinguished phiJosopher, and that he has only stated a few facts which deserve attention in order to be explained, rather than exposed any glaring discrepancy between those doctrines and the general appear. ances of the earth's surface.

Among the most important of the notices which are collected in this essay, we are inclined to enumerate those which respect the arrangement of mountain groups. In the third volume of Professor Jameson's work on mineralogy we are taught to believe that there is a certain order and regularity in the collocation of mountains; that where a group is viewed as a whole, it appears highest in the middle, and that this highest part extends through the whole group without being intersected. The lateral chains, it is added, shoot on both sides from the high mountain chain, and of these the most considerable is that which rises from the high mountain chain itself, and reaches to the foot of the group*. There are also two chief kinds of vallies analogous to the mountains, called the principal, and lateral or subordi

See Jameson, vol. ii. p. 11, &c.

nate.

nate. The principal vallies stretch without interruption from the high mountain chain to the foot of the mountain group, and those only are principal vallies that reach this point: the others, which merely extend from a mountain chain to a principal valley are subordinate*. We were not without suspicion that Werner and his pupils had reduced the mountains and vallies to greater order in their system than they are to be found in nature, and our suspicion is confirmed by the following

remarks.

"To begin with the Alps, which are not only the most remarkable assemblage of mountains in Europe, but have been examined and described more accurately than any other, it does not appear either from the maps of Weiss, or from the observations of Saussure, that there is any thing like that regularity of parallelism in the vallies of those mountains, which one is led to expect from the general theory of Werner, nor any thing like that regularity in the succession of the strata pointed out by the same theory. So far from it, that after the lapse of many years spent in a most laborious examination of them, with every assistance and every qualification necessary for the purpose, Saussure came to this conclusion; that there is nothing constant either in the order character, direction, or degree of inclination, of the strata composing that majestic assemblage of mountains: nothing, in short, constant in them but their variety t. On another occasion also he confesses that in viewing the group placed beneath his eyes from one of the highest summits near St. Gothard, the direction of the vallies did not appear to have any constant correspondence with the bearings of the strata; being sometimes placed parallel with, and sometimes at an oblique or even a right angle to them t. Again, he observes of the primitive mountains of Italy, Switzerland, and Savoy, that though at a great distance they appear to have that regular arrangement which has given rise to the term chain; yet this is a false impression, which vanishes upon a closer inspection §: and in another volume he asserts, that the chains of the Apennines near Genoa have no regularity either in their own direction, or in the direction of their accompanying vallies . The immediate group of Mont Blanc, the Aiguilles of Chamouni, and the group which is to the south-west of Mont Blanc, are not at all connected with each other ¶ and Mont Blanc itself, though the highest summit of the Alps, is not in the centre of the mass of primitive mountains which surround it: for on the side of Italy there are many more high summits than on the side of Savoy; so