It 



MOUNTAIN LIMESTONE. 



MOUSE. 



countries an of more value than in England. In the south of 

 England imperfect coal-beds called Culm replace the limestone. TbU 

 alao occurs in Russia and elsewhere. In Ireland this rock i abundant, 

 and the tries of beds are terminated by a peculiar sandy deposit 



The Culmiferous Series of Devonshire occupies a great trough, the 

 axis of which ranges east and west and extends for about SO miles, 

 with a breadth of between 30 and 40 miles. Crossing the edge of 

 this trough, we find a black limestone, overlaid by siliceous flagstones; 

 and these are followed by sandstones and carbonaceous and calcareous 

 shales, which gradually become harder, and pass into siliceous bands 

 of a dark colour, with earthy carbonaceous partings, surrounded by 

 a regular thick-bedded sandstone, resembling the gritstones of the 

 coal measure*. 



The beds, the order of whose superposition has been just mentioned, 

 form, with a black carbonaceous shale and a black limestone, the 

 lower subdivision of the whole Carboniferous System, as developed in 

 the south-west of England. The order is somewhat different however 

 towards Dartmoor, for there an irruption of granite has taken place 

 since the deposition of the strata, and the vicinity of the crystalline 

 rock has produced confusion and violent distortion. Notwithstanding 

 this, and the frequent repetition of these beds by faults and disturb- 

 ances, they are satisfactorily proved to be of great thickness ; but they 

 contain few fossils, and differ in lithological character from the rock, 

 probably of the same age, in the middle and north of England. 



The upper Culm-Measures of Devonshire are the newest beds of 

 the district, and occupy nine-tenths of the whole surface of the 

 carboniferous deposit This group is composed of sandstones and 

 indurated shales (the latter containing the culm), and is of great but 

 unascertained thickness, being perpetually interrupted, coiled upon 

 iUelf, and repeated over again, forming an incredible number of 

 anticlinal and synclinal lines, all of them ranging east and west, 

 parallel to the strike of the beds. 



There is however no difficulty with regard to the general order of 

 superposition, or the extent and real thickness of this pai-t of the 

 deposit; for both on the northern and southern outskirts of the 

 formation a great ascending series is seen, throughout the whole of 

 which the dip is tolerably regular. 



The sandstones of this group are generally close-grained, and of a 

 gray or greenish-gray colour, passing occasionally into flagstone and 

 laminated arenaceous shale, with fine ripple marks at the partings. 

 The shales vary in appearance from sandy beds to soft slaty clays, 

 not to be distinguished from the common coal shales ; and amongst 

 these latter are occasionally found dark carbonaceous bands, con- 

 taining obscure vegetable markings discoloured by pyrites. 



Such are the prevailing characters of the beds which form the 

 Ciiluiiferons Series of Devonshire : these beds being the true repre- 

 sentatives of the Carboniferous System. Notwithstanding the general 

 paucity of fossils, one or two species of shells are not to be dis- 

 tinguished from species well known in the Mountain Limestone ; and 

 the result of a comparison of the remains of plants from the culm, 

 with those commonly met with in rocks of the carboniferous period, 

 tends yet more strongly to establish the contemporaneity of the two 

 deposits. Considering the thickness of these Culm-Measures in 

 Devonshire, they might represent the whole mass of the Mountain 

 Limestone ; and the different mineral character of the rocks dependent 

 on the circumstances under which they were respectively formed, 

 might account for considerable alterations in the fossils, and must 

 have had great influence in modifying the forms of animal life. 



The Carboniferous System, as exhibited in Yorkshire and Derby- 

 shire, consist* of a magnificent development of Mountain Limestone, 

 to whose presence the picturesque scenery of those counties is due ; 

 the limestone being partly overlaid on the east, west, and north, by 

 the millstone-grit The lower part of the millstone-grit however is 

 sometimes represented by a series of laminated and often bituminous 

 shales, which rest immediately on the limestone, and contain some 

 bands of iron-stone, and a few thin black limestones ; while the upper 

 part consists of several hundred feet of pebbly grits and other sand- 

 stones alternating with thin bad coal. 



Farther north, and in the north-western part of Yorkshire, the 

 Mountain Limestone becomes a still more important and prominent 

 member of the Carboniferous Series, and is capable of local sub- 

 divisions. It is here subdivided into two groups, whose total thick- 

 new is about 1 800 feet Of these two the lower, the Scar Limestone, 

 forms bold bluff precipices, and is pierced in many places by large 

 natural caverns ; and both here and in the upper stratas (the Yore- 

 dais Iloclu), the limestone is remarkably different from the contempo- 

 raneous beds in the south, containing thin seams of coal, sometimes 

 worked, and divided into several beds by partitions of grit and shale. 

 The Yoctdale Rocks thus contain at least five distinct beds of 

 limestone, alternating with freestones, flagstones, Ac., and attaining a 

 thicknest of as much as 1000 feet In the north-west of England, 

 where the Mountain Limestone is developed in the same manner, the 

 upper beds of the scries, the millstone-grit and the true coal measures, 

 are scantily exhibited ; but in the north-east, as in Northumberland, 

 the Scar Limestone is much broken by the interposition of pebbly 

 grita, shale*, and coal-seams, which entirely change the character of 

 the formation. 



In Ireland the Mountain Limestone occupies an important place, 



and consists of two great bands of limestone, with a considerable 

 thickness of shale and argillaceous limestone and sandstone inter- 

 spersed, which are known by the name of calp, or calp-slato. It u 

 chiefly however in the northern and middle districts that the calp is 

 found, and it gradually thins out towards the south. Beneath the 

 lower limestone another series of schistose beds (the Carboniferous 

 Slate) occurs, and this rests on sandstone beds, often alternating with 

 shale, and occasionally with limestone. The Carboniferous Slate of 

 the south of Ireland differs in litliological character from that of the 

 middle and northern regions, but from the evidence of fossil*, tbo 

 two must be looked on as contemporaneous. 



On the continent the carboniferous beds are similarly developed ; 

 the lower beds in Westphalia passing into calcareous shales, contain- 

 ing fossil remains of the carboniferous type. These therefore are 

 assumed as the base of the Carboniferous System. They are imme- 

 diately succeeded by a group of black imperfect limestone and 

 siliceous schists (Kiesel-Schiefer of the Germans), considerably ex- 

 panded and traceable for some distance, and looked upon as the 

 equivalents of the English Mountain Limestone, the underlying beds 

 representing the shales occasionally met with in Eugland when the 

 sequence to the older rocks is complete. 



The Black Limestone is extremely carbonaceous, argillaceous, and 

 fetid, and it corresponds so entirely in mineral character with the 

 Culm Limestone of Devonshire, that the description of the one rock 

 might almost serve for the other, not merely as regards its y 

 appearance and lithological character, but alao because the organic 

 remains the Ooniatites and Potidonicc with which the rocks in 

 Devonshire are loaded, are in Westphalia also by far tho most abundant 

 fossils of the deposit On the continent however, the Culm Limestone 

 passes upwards into another limestone of a lighter colour, an<l th: 

 bed contains all the most characteristic fossils of the true English 

 Mountain Limestone. 



Advancing still farther eastward wo find in Russia that the lower 

 carboniferous beds consist of incoherent sandstone, alternating with 

 a bituminous shale, which sometimes contains thin bands of impure 

 coal and impressions of plants ; the whole being surrounded by various 

 beds of limestone, which form the central group of the Carboniferous 

 System. Of these beds, the lowest is usually of a dark colour, as in 

 other parts of Europe ; but the middle, and most extensive, differs 

 entirely from any contemporaneous rock, being of a milk-white colour, 

 resembling chalk, and loaded with flints. It is also of considerable 

 thickness, and extremely fossiliferous, and alternates with beds of 

 compact yellow maguesian limestone, and bands of red or greenish 

 shale or marl, while associated with it there ore splendid masses of 

 white gypsum and thin bands of limestone interstratifieTJ. The third 

 or upper division of the series is scarcely less remarkable than tho 

 central, being almost entirely made up of myriads of fossil bodies 

 (called Fusulina) resembling grains of wheat, and forming u limestone, 

 which is of considerable thickness, and appears in the lofty cliffs which 

 occupy the banks of the Volga, and also in the coal region between 

 the rivers Dnieper and Don. 



In Northern Russia, and in the upper beds of the Volga, the < 

 limestone of the Carboniferous System is totally devoid of coal, 

 which is found in shales and sandstones, interstratified with thin courses 

 of limestone in the lower part of the series, and in this respect ex- 

 hibits a resemblance to the lower beds of the Mountain Limestone in 

 Yorkshire. In the south of Russia, on the other hand, the central 

 beds of the Carboniferous System are occasionally productive of good 

 bituminous as well as authracitic coal, offering in some points very 

 striking analogies in mineral condition to the great South Welsh basin. 

 The northern beds are nearly horizontal, but the coal-field in the 

 south appears to have been disturbed, and to have been broken up by 

 faults. 



North America presents eome interesting points with respect to 

 the rock now under consideration. The Carboniferous Series of Penn- 

 sylvania is based upon massive sandstones, conglomerates, and shales, 

 overlying a bed of fossiliferous limestone. Resting upon this group, 

 which is of great and uniform thickness, there is a deposit of red 

 shale, which varies in thickness from 3000 feet to less than 100 feet, 

 and is supposed to thin out and disappear to the south-west; and this 

 is partly overlaid and partly replaced by a hard coarse conglomerate, 

 very thin towards the north-west, but rapidly swelling out and 

 becoming from 800 to 1200 feet thick towards the south-east. None 

 of these formations contain profitable coal, although the remains of 

 plants are found in them, and a few seams, about a foot thick, 

 occur in tho red shales. The coal-measures themselves form the 

 uppermost part of the series, and consist of micaceous sandstones, 

 arenaceous, argillaceous, apd carbonaceous shales, and valuable beds of 

 limestone. 



In other parts of the same wide area the Carboniferous Series mani- 

 fests similar peculiarities of structure. Thus, in Nova Scti 

 elsewhere in Canada, the lower beds consist of Carboniferous Lime- 

 stone ; but at Ca| lireton the millstone-grit appears to terminate the 

 sequence. Newfoundland also, which presents not less than 000 

 square miles of country, occupied by contemporaneous beds, has 

 hitherto afforded no coal. 



(A luted, Eltmcntary Couric of Gtoloyy.) 



MOUSE. 



