coincidence between two independent observers, is no slight confirmation both of the fidelity of their observations, and of the correctness of the hypothesis which they have severally deduced from them.

The error of some of the leading disciples of the Wernerian school in this country appears to be, that they already consider as established, with respect to the whole exterior of the globe, a principle which, at the utmost, is proved to a limited extent only. Yet, even in the present state of our knowledge, the facts brought to light by modern investigations, respecting the corresponding structure of very distant regions, are so remarkable, as to induce us to allow, not only the existence of a very strong resemblance between the rock formations of the globe in general, but an analogy at least, formerly unsuspected, in their successive order; and to withhold our dissent, until we are pos-. sessed of a greater body of evidence, even from the sweeping generalization of Werner. This order, it is true, is much less distinct in the older and primary rocks, perhaps also less determinate, and certainly much more difficult of development, than that of the more recent stratified formations: In the latter, we are sure that it is already proved to exist in Ergland, and some other countries of Europe. And if Geology at the present day deserves, in any thing, the name of science, it is in the approach which has been made to the establishment of the more general law which that succession implies.

That some such general law in the arrangement of rocks should actually be discovered, is what we think might have been expected, à priori, from the uniformity which is in other respects observable in the mineral kingdom. The chemical composition of the species of minerals, is determinate, not merely in the nature and number of their ingredients, but probably even in the numerical proportion of their elements. These simpler bodies, again, thus similarly constituted, are grouped together in the compound rocks, not with endless variety, but in aggregates, of which the number at present known, and probably the whole number, is very small; and, however dissimilar. the climates, or remote the quarters of the globe in which these aggregates occur, they are always found to possess considerable uniformity of character. The mind, therefore, is almost tempted to advance another step in the agalogy, and to expect that the arrangement, as well as the characters and composition of these aggregates, will have a certain steadiness and uniformity: And this expectation, while it ought to put us on our guard against deception as to the evidence, may also diminish our hesitation to admit, upon sufficient proof, what otherwise might seem very extraordinary.

A very important exception, however, to this regularity of arrangement, is found in the position of that great class of compound rocks, which includes all those of the Trap family, the porphyries, syenite, and some at least of the granite formations of Werner. The compounds of this tribe, in general, agree, not only in possessing the characters of very decisive crystallization, and in being wholly destitute of organized remains, but in exhibiting, at their junction with the stratified substances, the most obvious marks of violent disturbance and irregularity: And the trap rocks, in the form of large and rumerous veins, are found to traverse, indiscriminately, ail the other more regular formations. It is impossible, then, to believe, that the same laws have governed the disposition, both of these compounds and of the strata which contain organic remains, and exhibit greater regularity of structure: And every arrangement which assigns to both a common origin, or attempts to include the Trap, and other similar formations, in the general series of rocks, must, in itself, be defective, and even radically inconsistent. The capital mistake of Werner, (to which he was led, no doubt, by his erroneous theory), is, that he has attempted such a combination, and neglected these demonstrations of violence and disturbance.

In England, although the vicinity of the metropolis wants the more striking features which render the positions of Edinburgh and Dublin so interesting to the geologist, the series of rocks is fortunately such as to exhibit, very distinctly, the order of their succession: And the coincidence between the topographical features, and the geological disposition of the country, is, in several respects, of the most impressive character. The beautiful regularity of the long continued line, as it were, of coast, which is seen from Shotoverhill, at the termination of the chalk strata to the east of Oxford, has no doubt powerfully assisted the zealous geologists of that University, in making converts to their favourite pursuits: And it is impossible, while contemplating the general mass of the eastern portion of England, to learn that the elevated ranges, of several miles in extent, which, in so many instances, strike the eye, are formed by the emergence of certain distinct uniform strata, without feeling a desire to investigate the laws that have produced this regularity. It is, accordingly, to the development of facts like these, that the labours of geologists are at present everywhere directed: And this constitutes, in truth, the only method of arriving at what has been so long sought after,-a rational theory of the earth.

Those who are the best acquainted with the history of other

branches of science, will be the least disposed to regard the province of inquiry thus restricted, as unimportant or uninteresting; or to regret the seclusion of the naturalist from those more easy and tempting speculations which, till of late, it has been the fashion to dignify with the name of Geology. The most sublime discoveries, and the inventions most useful to mankind, the astronomical system of the Universe, the steam-engine, the safety-lamp, are all the result of long-continued researches, ennobled by their object, but abstract, severe, and laborious in their detail, and in themselves not at all more attractive than the minute comparison of fossil remains, or the most fatiguing pursuit of the ambiguous relations of rocks, amidst indistinct appearances, and through widely extended districts. In the mean time, Geology has this great advantage, of which not even Botany partakes more largely, that it leads continually to healthful and active exertion, amidst the grandest and most animating scenery of Nature, and that, demanding, indispensably, the combination of labour, and the interchange of acquirements, it gives rise to a frankness and warmth of communication amongst its cultivators, which renders the collateral results of friendship and association some of the most delightful of its fruits. There are few, indeed, of those who are engaged sincerely in the study of any department of natural knowledge, who will not testify, that many of those enjoyments which are remembered with the greatest satisfaction, have originated in the unreserved and candid intercourse arising from the common pursuit of truth.

The volume which has suggested these observations, contains, in the whole, fifteen different papers; of which, ten only are properly Geological,―eight relating to the structure of England,— and two to that of Foreign countries:-the rest are principally devoted to Mineralogy. The first paper in the volume is a very long one, of 111 pages, On the Geology of the Island of Sky, by Dr M'Culloch, of which we had prepared an abstract; but, perceiving that an additional memoir of the same kind, upon the same subject, has recently appeared in the 4th volume of the Geological Transactions, we shall defer our account of the whole until a future occasion.

The next paper that we shall mention, is certainly one of the most valuable which has been published by this Society, On the Geological features of the North-Eastern Counties of Ireland,from the notes of Dr Berger; with an introduction and remarks, by the Rev. W. Conybearc. It explains very clearly the structure of one of the most remarkable Basaltic districts in Europe; and establishes the identity of some of the strata in the north

of Ireland, with those of the eastern part of England, and of some other countries. The paper is illustrated by two instructive maps, and by a very interesting series of sectional views for more than fifty miles along the Basaltic coast, with observations by Mr Conybeare, and Mr Buckland, Reader in Mineralogy at Oxford; the former of whom appears to have discharged the duty of editor of Dr Berger's papers, with the greatest judg ment and candour.

The portion of Ireland which is here described, includes the counties of Derry, Antrim, Armagh and Down, with parts of Tyrone and Lowth, and is marked by three distinct groups or systems of mountains.-1. The Southern portion of the district consists principally of those of Mourne, in the county of Down, of which the highest summit, Slieve Donard, is 2654 feet above the sea. The prevailing rock is granite; but some lesser elevations on the north and east of the Mourne mountains, are primitive hornblende and greenstone; and to the north and north-west, a still lower chain, principally of grey wacke and greywacke slate, detaches this group from the Basaltic tract hereafter mentioned. -2. The second group, is situate above 30 miles N. W. of the first, principally in the county of Derry. Sawell, the highest summit, is 2557 feet above the sea; and the extensive tract around it is wholly primitive, mica-slate constituting almost exclusively nine-tenths of the district.--3. The third system comprehends two chains of hills, bounding on the E. and W. the valley through which the river Ban flows from Loughneagh to the ocean; it is formed entirely of an enormous platform of basalt, from beneath which, at an interval of 30 miles from the primitive country, mica-slate again emerges at the N. E. angle of the county of Antrim.-The exact correspondence between the structure of the portion of Ireland here described, and the opposite parts of Scotland, which is illustrated in the papers by a coloured geological sketch, leaves no doubt of the former continuity of the Scotch and Irish coasts.

The primitive districts of Mourne and Londonderry, are described in the paper, and the topographical distribution of the primary and intermediate rocks is given; but their boundaries are not minutely traced; and it is from the 3d, or Basaltic country above mentioned, that the memoir principally derives its interest. The surface of this tract appears to form a sort of basin, with its lowest point near the centre of the trough or valley of Ban; the hills presenting abrupt declivities to the east, north, and west, but sloping gently inwards in every direction. The summits within this area are in general detached and distinct: Knocklead, the highest point at the north of the eastern range, is 1820 feet above the sea; and Divis on the south, 1475 feet. In the

western chain, Craignashook, at the southern extremity, is 1864 feet above the sea, and Benyavenagh, the extreme mountain on the north, 1114. The whole surface of the district is covered with a vast stratified mass of Basalt, about 540 feet in average thickness, and not less than 800 square English miles in extent. The strata upon which this mass reposes, agree precisely with some of those which are found immediately above the coal, to a great extent, in the south and east counties of England; but those in Ireland do not reach beyond the verge of the Basaltic mass, by which they seem to have been protected from the agents that have removed them in other situations. The whole series is traversed by numerous dikes of trap. The rocks of the several districts described in this paper, succeed each other in the following order, beginning with the lowest

The rock most widely distributed in the primary country is the mica-slate, No. 2, which is in some places succeeded immediately by a red sandstone, No. 10 or 13; the former of these numbers appearing, according to Dr Berger, to alternate, in some instances, with greywacke. The limestone, No. 11, is of great importance in the local geology of Ireland, as it appears to constitute a portion of the great calcareous formation, which may be traced from Dublin, through several of the midland counties, and to be the rock upon which the great coal districts of Kilkenny and Lough-Allen, as well as those of Dungannon and Coal Island, described in this paper, are found to repose.* The

* A mistake, of considerable importance, occurs at p. 159, where Dr Berger mentions, that all the coal in Ireland to the north of a line drawn through Lough-Allen, from the cast to the western coast, is Slate coal, but to the south Cannel coal-the latter being evident. ly intended to signify Kilkenny coal, a substance perfectly distinct, which contains no bitumen.