second misconception of the language of Prof. Buckland is no less remarkable. "The new red conglomerate of Exeter is the red sandstone of French mineralogists, or todte liegende of German mineralogists; it is the first secondary (floetz) sandstone; that is to say, the sandstone of the carboniferous tract, which is intimately connected with secondary porphyry, and hence the latter is called the porphyry of the red sandstone."* But the position of Prof. Buckland is directly the contrary; namely, that the red conglomerate of Exeter does not at all belong to the carboniferous series, and is altogether of an origin posterior to it, and hence denominated new. With respect, however, to the real period, to which the red conglomerate in the vicinity of Exeter may more appropriately be referred, should its connexion there with the amygdaloidal trap be ascertained beyond dispute, I confess I should rather side with the opinion of M. von Humboldt; namely, that both belong to the carboniferous series. But should there be no such decided connexion, it may yet appear that the amygdaloid belongs to the transition tract of that country, and the conglomerate itself to the gypseous or new red sandstone, that is known to prevail in that part of the kingdom. I have more than once found it necessary to show, that English geologists have misunderstood the true import of the older red sandstone group, or rothe todte liegende, of German authors; and additional evidence of this fact is to be found in the construction put upon these terms throughout the very interesting and important work of M. von Humboldt. See in particular the first division of the Terrains Secondaires, p. 205, et seq. from which, in addition to preceding extracts, I select only the following:-" It is difficult to assign a general type for the order of the different beds which constitute the great formation of coal, red sandstone, and porphyry (with interposed beds of amygdaloid, greenstone, and limestone). The coal appears most commonly below the red sandstone, and sometimes it is evidently placed either in this rock or in the porphyry.”+ This last sentence appears more particularly referable to certain parts of Germany, where only a portion of the carboniferous series is displayed, e. g. in Thuringia; but from such merely local facts no general inference can be drawn. "Sometimes the great deposit of coal is not covered by porphyry and red sandstone sometimes it occupies great basins surrounded by hills of red P. 157. "Le nouveau conglomérat rouge (new red conglomerate d'Exeter) est le grès rouge des minéralogistes francois, ou todte liegende des minéralogistes Allemands; e'est le premier grès du terrain secondaire, c'est à dire le grès du terrain houiller, qui est intimement lié au porphyre secondaire, appelé pour cela porphyre du grès rouge.’ See also p. 205. ; + P. 209. "Il est difficile d'assigner un type général à l'ordre des differentes assises qui constituent la grande formation, § 26. La houille paroit le plus souvent au-dessous du grès rouge; quelquefois elle est placée évidemment ou dans cette roche ou dans le porphyre." c 2 sandstone and porphyry, and presents in its roof only alternating beds of slate-clay and carbonated shale, the former containing numerous impressions of ferns. Thin beds of coaly shale, beds of quartzy sandstone passing into granular quartz, of largegrained conglomerate (coal measure conglomerate), and of fetid limestone also, are met with in the midst of the slate-clay before the coal is attained."* On the other hand, it is equally certain, that Continental geologists have misconceived, in some instances, the purport of the language employed by English writers. Hence has arisen a double confusion; when, after all, if the language of each had been correctly apprehended, there would have been as little discrepancy in description as there is in the appearances of nature, since the facts themselves are perfectly reconcileable to each other. To attempt to clear away difficulties and dispel obscurity is both an irksome and ungrateful task; and the love of truth alone has impelled me to it. If it shall be found that I have in any degree succeeded in throwing a clearer light upon a complicated subject, my purpose will be fully answered. The researches of M. Constant Prevost, an eminent French geologist, and FMGS. who is at present engaged in examining the geological relations of this country with a critical eye, will, I have not a doubt, conduce to the same desirable end. I have upon former occasions remarked, that all the established relations of the old red sandstone, carboniferous limestone, and coal formation, to each other, as founded upon the researches and descriptions of naturalists in different countries, prove that they constitute one group of the same era; yet varying much in the modes of their association, as being found in one tract distinct from, and in another more or less interstratified with each other. The following view, which may be of some value in reference to practical and economical purposes, will be found to embrace a summary of those relations. 1. Old red sandstone, carboniferous limestone, and the coal formation, in separate and distinct succession, not interstratified upon their several confines; e. g. the general case in Ireland. This may be considered as the distinct type of the series. N. B. The bed of sandstone and conglomerate, found in some tracts interposed between the limestone and the coal measures, * P. 207. "Souvent le grand depôt de houille n'est pas recouvert de porphyre et de grès rouge. Souvent il est placé dans les basins entourés de collines de grès rouge et de porphyre, et n'offre dans son toit que des couches alternantes d'argile schisteuse (schieferthon), tantôt gris-bleuâtre, tendres et remplies d'empreintes de fougères, tantôt compactes, carburées (brandschiefer) et pyriteuses. Des minces strates de grès charbonneux kohlenschiefer), de grès quartzeux passant au quartz grenu, de conglomérat à gros fragmens (steinkohlen-conglomerat), et de calcaire fétide, se rencontrent au milieu du schieferthon avant qu'on atteigne la houille." and designated in England as the millstone-grit, is wanting in Ireland. N. B. This peculiar application of the term millstone-grit is bad as a distinction, since a similar compound is generally found in beds in the fundamental or old red sandstone, and in some countries also frequently interstratified with the coal measures, e. g. in Germany. 2. A base of old red sandstone, supporting limestone, which alternates with sandstone, a considerable bed of the latter, with conglomerate, forming the immediate foundation of the coal measures, which are distinct; e. g. the Gloucestershire south coal basin. N. B. The more common coal bearing measures are in this basin separated into a lower and an upper series by an intervening thick bed of reddish sandstone, locally known by the name of Pennant-stone. N. B. A similar occurrence, on a larger or smaller scale, is not uncommon in Germany, and when the red sandstone thus occurs immediately under the magnesian or alpine limestone (with its calcareous or new conglomerate, the weissliegende), it is known by the name of todte liegende, or rothe liegende, or rothe todte liegende, in the same manner as these terms are applied to the fundamental red sandstone when also directly covered by the calcareous conglomerate and magnesian limestone. But the term rothe todte liegende has also been often erroneously applied, as already noticed above, to the calcareous or new conglomerate itself.* 3. A base of old red sandstone, supporting and alternating with some beds of limestone, succeeded by a coal formation, composed, in an ascending order, as follows: a. Of coal measures alternating with limestone, and with reddish sandstone, the coal being inconsiderable in quantity. b. Productive coal measures, alternating with numerous beds of limestone. * M. von Humboldt correctly distinguishes the weissliegende, as the bed which intervenes between the coal formation and the zechstein, or magnesian limestone (see p. 224 of the Essai). It thus corresponds with the calcareo-magnesian, or new conglomerate of England, appearing as its only representative. On the other hand, however, both M. von Humboldt and Dr. Boué speak of the zechstein, or magnesian limestone, as occurring sometimes interstratified with the coal measures. This is a position utterly at variance with all experience in the British Isles, and seems quite untenable, if we consider that the calcareous conglomerate, or weissliegende, is commonly found in an unconformable position, overlying both the coal measures, and the carboniferous series in general; being the first member of a new series; namely, of the gypseo-saliferous. In the instance quoted, e. g. in Lower Silesia (p. 34, 213, &c.) it is true that, in the year 1802, M. von Buch considered the limestone in question as zechstein, and as such as of an origin posterior to, and placed above the coal formation; but M. von Raumer in 1819 clearly showed that this limestone was repeatedly interstratified with the coal measures, and therefore not zechstein; and certainly no two series can be generally more distinct from each other than the carboniferous and the gypseo-saliferous series. Other instances cited, probably rest upon no securer foundation than misconception, or fallacious description. c. Coal measures, abundant in coal, but free from limestone. E. g. in the Scotch great coal tract. 4. A base of old red sandstone, supporting limestone, which not only constitutes the foundation of the coal formation, but alternates with the coal measures, often forming the immediate roof of the coal seams: e. g. the Glane coal basin, described above. 5. A. base of the same old red sandstone, supporting a coal formation, composed, in an ascending order: a. Of productive coal measures alternating with beds of sandstone conglomerate. b. Of coal measures alternating with limestone. E. g. the Sarre coal basin, described above. N. B. The coal measures of this basin are overlaid on the W and S by the new red or saliferous sandstone; so that if the series of coal measures be continued in that direction, and toward which they dip, they are withdrawn from observation. Could we follow them, it appears not improbable that the succeeding coal measures might be found free from limestone. But be this as it may, it is remarkable that in this coal field, the greatest number of the coal seams are found above the fundamental red sandstone, and beneath the limestone bearing strata, being thus directly connected with the former. The carboniferous series of all countries, whose members are complete, will probably be found referable to one or other of the preceding modes of association. In addition to those which relate to the alternation of the carboniferous limestone with the coal measures, may be cited analogous appearances in Silesia and Hungary, as described by MM. von Raumer and Beudant. The New Continent also presents, it seems, similar relations; e. g. in the coal formation of the Ohio, in the great basin of the Mississippi, where coal seams are represented as occurring both above and beneath the limestone.* The preceding examples refer to tracts where all the members of the series are present; but in some districts, the carboniferous limestone is found altogether wanting, the coal formation being directly connected with the old red sandstone; while in others, both the limestone and old red sandstone being absent, a simple coal formation is only met with. But in all cases, the series, whether complete or incomplete, reposes either on transition, or on primary tracts, or on both of these conjointly. The occasional association of trappean, amygdaloidal, and porphyritic rocks, both separately with the individual members, and conjointly with the series in general, is now too well known to require more than the simple notice of the fact. See the Account of an Expedition from Pittsburg to the Rocky Mountains in 1819 and 1820, by Edwin James, Botanist and Geologist to the Expedition. London, 1823. ART. IV. Corrections in Right Ascension of 37 Stars of the Green wich Catalogue. By James South, FRS. a Arietis July 1+ 2.79" + 3.27"+2:33′′ + 1·92′′ + 1·76" + 2·00" + 1·24" + 1·81" + 1·47′′ 49 50 52 53 28 60 24.54 22 73 50 86 84 50 2.02 29 63 25.30 25 76 04 |