Collective works

“ It is impossible for any two portions of the same formation to be more entirely identified, by every external character and by the fossils and organic remains contained in them, than are these Irish beds, which have been frequently called white limestone, with the English chalk in the above places: there as in England the lowest beds are destitute of flints which the upper contain in abundance. ”

“ The numerous beds of coarse calcareous oolites, which in England succeed this green sandstone, are entirely wanting in Ireland, and the mulattoe reposes immediately on the lias limestone. Analogous circumstances are not however wanting in England. In the neighbourhood of Lyme Regis, in Dorsetshire, the sandstone has extended itself over the cut goings of the oolites, rests upon the lias in a manner similar to that just described; and as it is covered with beds of chalk, the whole section affords an exact counterpart to that presented by the Irish series. ”

“ To preserve uniformity in the colours which represent the different rocks I have here also tinged the limestone blue. It is white in nature. It serves to show the entire loss of the stratified character which the limestone so often undergoes in the vicinity of the granite. Specimens from this junction are also in the Society's collection. ”

“ In the eastern part of Tyrone which intervenes between these two systems of mountainous ground, a coal formation occurs associated with that variety of limestone which is usually found underlying or alternating with the coal measures in Great Britain.
The position of this coal field offers a new analogy with Scotland, where the interval between the southern and northern mountains is principally occupied by a broad zone of rocks connected with the coal formation, upon which are placed those vast overlying masses of trap formation which constitute the Campsie hill, the Ochills, &c. ”

“ The river here divides the stratified rocks from the granite, and has exposed the various junctions which are laid down in the map and described in the paper. It is easy to see how these will sometimes consist of limestone, sometimes of schist or of quartz rock, and sometimes of all the three substances, with the granite. ”

“ The average thickness of the chalk formation in Ireland may be estimated at between two and three hundred feet; the upper beds seem to have been partially redissolved before the basaltic mass was deposited upon them, since along the line of junction a confused aggregation of chalk flints exists, imbedded in the lowest member of the trap deposit, which is usually a bed of ochreous bole: the flints so imbedded have usually themselves acquired a red tinge, apparently by percolation, from the oxidated iron of the stratum in which they lie. ”

“ In Carintogher and Cragnashoack the chalk appears to be wanting, and the basalt to repose immediately on the sandstone; but in the insulated mass of secondary strata which cap the primitive mass of Slieve Gallion (on the south of the great valley of denudation, through which the Mayola flows) the chalk again appears underneath the basalt, and there attains its greatest elevation, being quarried at the considerable height of 1460 feet above the level of the sea, the deposit is however thin and the strata much split. ”

“ In a valley near Ballintoy, the inferior limit of the chalk is exposed, and a substratum of a bluish slate clay, containing gryphites and ammonites, (apparently the same which alternates with the lias near Glenarm) is laid open. The chalk is abruptly broken off on the east of White Park bay, in a little cove called Port Braddin. Here the basalt abuts directly against the chalk, and that arrangement of strata, so well known as constituting the magnificent range of promontories in the neighbourhood of the Giant's Causeway, commences. ”

“ The northern coast of Antrim seems to have been originally a compact body of limestone, (chalk) considerably higher than the present level of the sea; over which, at some later period, extensive bodies of vitrifiable stone have been superinduced in a state of softness. The original calcareous stratum appears to be very much deranged and interrupted by these incumbent masses. In some places it is depressed greatly below its ancient level. ”

“ The greenstone slate of the Mourne mountains contains apparently no crystallized hornblende in the basis, though it is disseminated through the latter, as is shewn by the manner in which it fuses before the blowpipe. I have remarked in it some crystals of glassy actynolite passing into hornblende, veins of quartz, magnetic and common iron pyrites. The basis sometimes approaches in its nature to clay-slate. ”

“ Near Ballycastle a broad valley opens into the interior towards wards the south and east. This valley is principally occupied by the red sandstone, which, in those directions terminates against the mica slate, forming the base of Knocklead (the round-backed mountain seen in the distance) and extending thus far in continuation of the primitive district already described in Cushleak. Between 4 and 500 feet on the ascent of this mountain, a bed of primitive limestone may be traced. Above this, through an interval of about 400 feet, the strata have not been ascertained ”

“ Towards the west the chalk runs far out to sea, forming a sharp and narrow point of land, of which the greatest height is about 70 feet. The isthmus which joins this point with the main land, is completely broken through. The ruins of an ancient tower rise above this chasm, on the sides of which the course of an enormous whin dyke may be traced; and the whole promontory is shattered in every direction, masses of basalt (sometimes mingled with chalky debris and flints) protruding through numerous fissures. ”

“ The N.E. coast presents a small coal formation precisely analogous to that of Ballycastle, with beds of breccia and of red sandstone resembling those which occur in the Antrim coast near New own Glens; this sandstone forms the prevailing substratum through the whole south of the island, where it is covered by a singular columnar clay porphyry, and by greenstone, both of which rocks are generally referred to the flœtz trap series. ”

“ I. Of all other formations, the least ancient are the least elevated; but this, the most recent of all, yet rivals the primitive mountains in height.
2. Of all other formations, the degree of consolidation decreases together with its age, their texture passing from crystalline through the several gradations of sub-crystalline, compact, coarse, and lastly earthy; while in this formation, even where it rests on chalk, the crystalline texture of the oldest rocks frequently recurs. ”

“ Augite usually accompanies greenstone and sometimes greystone. Steatite is almost exclusively limited to the prismatic basalt; and it is likewise the only heterogeneous ingredient I have observed in it. It exists in small round specks, of a bottle-green colour so dark, that it is not easily discernible from the mass itself: it has a dull and waxy appearance; is soft, the streak greyish.
Glassy felspar characterizes the clinkstone porphyry. Calcareous spar, zeolite, iron pyrites, and chalcedony usually occur in association with the preceding substances. ”

“ The solid strata are frequently traversed by veins and thin layers of calcareous spar: between them intervene many thinner beds passing into slaty marl.
The limestone itself somewhat varies in its characters at the different places where it occurs. In point of colour it passes from bluish-black to smoke-grey: the first variety is more compact, the lamellar concretions less evident, and it is sometimes traversed by veins of flinty slate; small quartz concretions are occasionally though rarely interspersed in it. I have seen in it crystallized iron pyrites ”

“ The cliffs of Cushleak ranging from the mouth of the Glendun river to Murloch bay present mica slate, containing subordinate beds of primitive limestone, syenite, and felspar porphyry.
The hills rising above these cliffs, as they approach Murloch bay, become covered with beds of red sandstone and chalk towards their summits, and some of the highest points exhibit caps of basalt. It is highly desirable that the slopes of these hills should be carefully explored ”

“ The slate clay at Mary Ann Pit contains impressions of aquatic plants, vegetable impressions similar to those of the Derbyshire collieries have also been observed in the Ballycastle district.
Clay ironstone occurs both in nodules and beds, and brown spar passing into sparry iron ore has been observed at the coal works of Ballycastle, where it forms a bed of some thickness traversing the cliff at a little depth below the principal seam of coal. ”

“ I. Tyrone: at Coal-island and Dungannon. II. Antrim: near Ballycastle. 1. Two Coal fields, as coal formations are usually styled in England, exist in the county of Tyrone, at no great distance the one from the other, viz. at Coal island and Dungannon; with the latter I am totally unacquainted: it is I believe, by far the most extensive of the two: whether they may be considered as connected and thus constituting but one single formation, I do not pretend to say.
The coal formation of Coal island is in an open part of the country, though with a gently waved surface. ”

“ In the Mourne mountains and adjoining districts an extensive formation of granite occurs, but neither here nor elsewhere in the north of Ireland can we recognize the same varieties of that rock which the mountains of Wicklow present. ”

“ Mulattoe, an arenaceous stone, with a calcareous cement, of a speckled appearance (whence its name) derived from numerous disseminated spots of green earth. It agrees altogether in its character and fossils with the green sandstone, which occurs in a similar geological position underlying the chalk in England: the thickness of this deposit appears to vary very considerably, and has not in any instance been precisely ascertained. ”

“ The sandstone formation may be traced from the south west extremity of the county of Antrim, where it joins that of Down, occurring between Moira and Lisburn, at Maherameslt, Spencer's bridge and Maheragall; it proceeds along the valley of the Lagan, extending into that of the Forth, a small river which becomes tributary to the Lagan near Belfast; from that town it occupies the road to Carrickfergus, whence it ascends the valley of the Woodburn, another brook discharging itself into Belfast Lough; it afterwards extends as far as Castle Chichester, in the island of Magee. ”

“ From the hasty survey which I was myself able to take of this spot, I can only furnish the following particulars:─ The total height of Cross Hill, in the north face of which the collieries are worked, is about 500 feet, of this elevation about 150 feet is formed by a cap of columnar green-stone, which reposes on alternating strata of sandstone and slate-clay, these extend about 150 feet in depth, and cover the bed of coal in which the workings are situated, and which occurs at an elevation of about 200 feet above the beach ”

“ These four formations which, together with the basalt, constitute the whole mass of the mountains belonging to the third system, cannot be estimated as possessing a less average thickness than from 800 to 1000 feet: the whole system appears at the north-eastern and south-western extremities to repose upon the coal formation, and its associated limestone, and this again on transition or primitive rocks. ”

“ From Blackhead the eastern coast of the peninsula of Magee exhibits a long and lofty range of basaltic cliffs called the Gobbins, extending nearly eight miles towards Portmuck at the north-east extremity of the peninsula; near this point the chalk emerges from beneath the basalt, and the lias from beneath the chalk. Hence to the mouth of Lame tough the cliffs cease, the hills rising with a gradual acclivity from the beach ”

“ Where the dyke traverses the great insulated mass of slate, it is very irregular both in thickness and direction. The works of Gob colliery have reached, this dyke 500 yards inland from the face of the cliff: the coal is altered by it to a considerable distance from its point of contact, being reduced to the state of a cinder, which can be employed only for burning lime. ”

“ It appears to constitute almost the whole mass of the Mourne mountains, whence it passes across Carlingford-bay into the county of Louth, extending to the summit of the Ravensdale mountains. It soon crosses the limits of Louth to enter into Armagh, composing part of the Faughel hills, whence it expands itself into a flat and elongated ridge, well known under the name of Slieve Gullen, forming likewise the Slieve Girkin or Newry mountains, and the lower and upper Fathom hills, of which the latter keep close to the right bank of the Newry river. ”

“ Imrie in the same publication; be represents them as universally covered by a thick mass of flœtz trap, divided into beds, partly amorphous and partly columnar. The trap formation of the north of Ireland consists principally of basalt divided into beds, partly amorphous and partly columnar; the latter variety resembles clinkstone in the property whence that rock derives its name; the basalt passes into greenstone, as may be seen in the mountain of Slievemish and other places; and it alternates with amygdaloid. A formation of clay porphyry also occurs in the center of the basaltic area. ”

“ Near Cookstown, grey sandstone passing into white occurs on the road to Dungannon, it extends beyond the bridge over the Blackwater river, the outgoings of the strata rise south-west 43° under an angle of 8°. There are other sandstone quarries one mile and a half from Cookstown towards Moneymore; a red variety is here found, it is finely granular, with a calcareous cement, the strata crop out south-west 53°, at an angle which varies from 13° to 25° as they increase in depth. ”

“ The strata lean on the east side of the Golding mountain dipping to the south east: they however rise to a very inconsiderable height upon its abrupt declivity.
There are quarries opened in a continual line to the extent nearly of one English mile, at the foot of the Golding mountain, the depth of the quarries varying from fifty to eighty feet: limestone is raised besides in other places nearer to the shore, at Cooley, Mullaghtre, and the Gan rocks.
This limestone is remarkable, because it alternates both with transition trap and with greywacke slate ”

“ The pillars of Fairhead, and the adjacent summit of Fairhead, are composed of greenstone containing augite.
Basalt passes into greenstone in the most imperceptible manner: in the first stage, the felspar exists under the form of short, scaly parts either white or greenish; the texture becomes more finely granular and crystalline; the fracture in the great is not into flat conchoidal pieces, but more usually into irregular and blunted fragments. This finely granular and almost compact greenstone is also more tough than common flœtz-trap. ”

“ The peninsula itself, which may be about a mile in circumference, is fenced with low cliffs on the west, north, and east; those on the west present a rudely prismatic greenstone; those on the north and east tabular masses of greenstone, overlying, and in some places appearing to alternate with, a very remarkable rock which has been the subject of much discussion among the supporters of opposite theories.
It is a flinty slate, exactly similar to the indurated slate clay which forms the wall of the Carrick Mawr dyke, in the Ballycastle collieries ”