[From Wood's Accout of IoM, 1811]
[This first chapter is probably the first geological description of the Island]
AN ACCOUNT OF THE ISLE OF MAN.
Situation and Extent of the Isle of Man. Etymology of its Name. A Sketch of its Mineralogy.
MAN is an island in the Irish Sea, distant from St. Bee's-head, in Cumberland, thirty nautical miles; from Burrow-head, in Scotland, sixteen miles; and from Strangford, in Ireland, twenty seven miles; the latitude of the middle of the island being fifty four degrees and sixteen minutes north. Its length rather exceeds thirty miles, and its mean breadth ten,
Etymologists are not agreed respecting the derivation of its name. Bishop Wilson supposed it to be an abbreviation of Manning, its present Manks appellation, signifying, in that language, among; this isle being surrounded by other territories. Some suppose it to be derived from Mona, a word which they imagine, but without sufficient authority, to have been used by Caesar to denote this islande(1) Mona and Monoida are classed by Ptolemy under the head of Irish islands Pliny informs us that Mona and Monapia lie between Ireland and Britain:(2) and the Mona of Tacitus is undoubtedly Anglesey; since he relates in his Annals the circumstance of the infantry of the army of Suetonius crossing from the main land in flat-bottomed vessels; and of the horse partly fording the passage upon the shoals, and partly swimming over. And, again, we are informed, in the life of Agricola, that the army under the command of that general crossed the straits without the assistance of any vessels, and so frightened the inhabitants by the boldness of such conduct, that they sued immediately for peace.
Perhaps the words Mona and Man may both of them be derived from the ancient British word môn, accented grave in Owen's dictionary, and signifying what is isolated.
This island is divided into two unequal portions by a chain of moderately high mountains running from north-east to south-west, broken at one part, between mount Kreevey and South Barrule. The most considerable summits are Snawfel and North and South Barrule, the two last forming its extremities. The height of Snawfel, as taken by the barometer, is five hundred and eighty yards above the level of the sea; and the two Barrules are inconsiderably lower.
The high land between North Barrule and Mount Kreevey gives rise to several rivers, the chief of which empty themselves into the sea at Ramsey, at Laxey and at Douglas. Ramsey river is the largest; and the flat country, through which it finally runs, permits spring-tides to produce their effect upon it two miles from the sea. The northern branch of Douglas river rises on the western side of Mount Garrahan. The northern side of South Barrule contributes a portion of its waters to Peel river, and another to the river of Glenmay. The southern side sends forth a streamlet, one of the branches of Castletown river, which joins the other branch, a little above Athol bridge, running nearly south. All the streams are very shallow; and smaller ones, not large enough in summer to turn a mill, are very frequent.
The northern portion of the island is a light sand, resting on a bed of common clay: the greatest portion of the island consists of a barren soil, resting on grey wacke-slate, and on clayslate: a small portion around Castletown is composed of lime-stone of transition: and the mountains are formed chiefly of strata of clayslate, much intersected by veins of quartz, and which seem to rest on mica-slate, a mineral that occurs on the sides and summits of several o' them, and which probably rests on granite.
The dip of the strata, whether of slate of lime-stone, or sand stone, is almost invariably south east. The chief metallic repositories are veins of lead and copper ores near Laxey, at Foxdale, and at Breda-head, near Port Erin.
Such is a general view of the distribution of the mineral productions in the island. I shall now give a detailed account of the individual mineralogy, beginning with the mountains.
North Barrule, the northern extremity of the chain, is composed of mica-slate, covered by clay-slate. The new road, from Ramsey to Laxey, is cut in the side of this mountain, and exposes its internal structure, which consists of mica-slate covered by a shining, clay-slate, formed of thin laminæ. The clay-slate covers it to the summit in saddle-shaped strata.
Snawfel, the next important one, is composed of the same materials as North Barrule. The clay-slate, which is more glossy, and of a more micaceous appearance, covers the mica-slate in mantle-shaped strata, leaving the latter projecting through them to form the summit. The mica-slate contains much quartz, which is often crystalised in transparent pyramidal crystals. The clay-slate on this mountain becomes less shining as we descend, that is, as are recede from the mica-slate, and gradually gives way to grey wacke-slate. This appearance is a very general one in primitive countries, the oldest strata of clay-slate gradually approximating the more crystalline appearance of the primitive rock on which they rest, as they approach it. The sides of Snawfel are generally covered, to the depth of several feet, with turbary, the surface of which is green with mosses and rushes. The verdure continues to the top, and is frequently studded with the snowy tufts of Eriophorum vaginatum and E. polystachion, (cotton grass.) Here and there the strata of the mountain are exposed to view.
Penny-pot (perhaps Pen-y.pont(3) ) is composed of clay slate to the summit, resting in all probability upon mica-slate. The clay-slate resembles exactly that of North Barrule in colour, lustre, and the thinness of its laminæ,. This is the most marshy of the mountains; And the ascent, even in dry summer weather, is consequently tedious and unpleasant
Mount Kreevey is very rugged and precipitous near the road from Douglas to Peel. The strata nearest the surface are glossy clay-slate, traversed by many large veins of quartz, which are often two or three feet thick, and generally contain a considerable quantity of mica. Micaslate lies immediately under the clay-slate.
South Barrule, the southern extremity of the ridge, presents on its north side many blocks of granite, composed of silvery mica, reddish white feldspar, and grey quartz. These are too numerous and too huge ever to have been transported by human art. Fragments of mica-slate make their appearance on several parts of the mountain, but the prevailing rock is a clayslate similar to that of Pen-y-pont. From these facts it is highly probable that the nucleus of this mountain consists of granite.
This arrangement may also be considered as that of the great mass of the island, except that, in the plains, the common clay-slate gives place to grey wacke-slate.
In tracing the strata from Douglas towards Castletown we find that the grey wacke-slate continues from the high land to the sea shore, without interruption, as far as the first creek, northward of Derby-haven. In approaching the shore from the mountains, the clay-slate becomes less and less shining, exhibiting more the appearance of a mechanical deposit, till it passes into grey wacke-slate. Here its fresh fracture is dull; and the strata, which, near Douglas, are highly inclined, dip only 10° or 15°. At this place we find a bluish grey limestone, containing impressions of shells and other marine exuviæ,. It lies over the grey wacke-slate. The line of stratification is distinct, and in some places filled up with a thin latter of white clay, which seems very pure. The clay does not in the slightest degree effervesce -with · acids. The limestone contains veins oil calcareous spar; and, along the coast, it is much corroded on its surface by the action of the weather. The strata are generally from one to four feet thick, dipping 10° or 15° towards the south west
A considerable portion of the lime-stone tract exhibits alternations of lime-stone with grey wacke~slate, the strata of which are but a few inches in thickness. This circumstance demonstrates the lime-stone to belong to the class of rocks denominated by Werner "rocks of transition." This lime-stone, in colour and in the organic remains which it contains, very much resembles the lime-stone of transition found on the mountains near Crook-Inn, on the Moffat road in Scotland. The clay found in the insterstices of some of the strata of lime-stone most probably arises from the decomposition of the grey wacke-slate by the constant action of the weather. Indeed this slate, where exposed to the air, is, for the most part, friable and crumbling.
With the small interruption of the isthmus and promontory of Langness, the lime-stone continues along the winding shore to the further part of Pool-vash bay. Here it is highly indurated, and rests upon a glossy clay-slate intersected by veins of quartz. A little to the south it becomes still more indurated, and is quarried, below high water mark, as a pretty good marble for tomb-stones, the formation of which is facilitated by the increased thinness of the laminæ. The steps to St. Paul's church in London are from these quarries, and were presented by Bishop Wilson.
A short sandy isthmus joins the promontory of Langness to the main land. The promontory and the islet of St. Michael are composed of grey wacke-slate, excepting a small tract, a few yards wide and some hundred yards long, on the north western side of the promontory, adjoining the sands of Castletown bay. Here we meet with a breccia, composed of rolled pieces of quartz in a siliceous base, resting on a glistening slate. Some of it approaches to horn porphyry.
The inland boundary of the lime-stone tract extends from the creek first mentioned to Balasalla, including that village; and thence, crossing the Castletown river, to Pool-vash bay. At Athol bridge, on the Castletown river, grey wrack-slate is found. Following the stream for a quarter of a mile we find lime-stone, and near it a quartzese rock, like that at Langness: but these are the only places where I have observed it. Continuing our descent, we find a small quantity of compact brown iron-stone, lying immediately under the breccia. It crosses the bed of the river near a mill. The breccia continues for about a hundred yards further, and then gives place to lime-stone.
Clay-slate appears again at Port to Murray bay, and is composed of very thin laminæ, with a silky gloss; and much traversed by veins of quartz. The surface of the layers leas that peculiar undulated appearance, which was, I believe, first noticed by Sir James Hall.
Clay-slate constitutes the upper rocky mineral to Spanish head; round, from thence, to Port Erin, and, with little interruption to Peel.
There is a quarry of a very tough clay-slate below high water mark at Spanish-head, which is raised in blocks, ten or twelve feet long, eight, ten, or twelve inches broad, and four, six, or eight inches thick. These are employed for purposes which, in other countries, are effected by beams of wood, as for gate-posts, and alpine bridges over streamlets.
The Calf of Man is a small island, separated from the main by a gut of about one hundred yards. The summit of this island is upwards of five hundred feet above the level of the sea; being nearly equal to the high land of Spanish head. The strata consist entirely of a glossy bluish-grey clay-slate, more inclined to the east, and less regularly stratified than the slate rock on the main. I was told that marble was to be found in the Calf; but it proved to be whitish quartz, found sometimes in detached masses; and frequently forming veins in the slate. There are several huge masses of slate rock separated from this island; one of which, the Borough, is perforated arch. The circuit of the Calf may be about five miles; its area, six hundred acres.
Between Port Erin and Kirk Arbory, near the latter place, and on the left hand side of the road, are the shafts of lead mines now deserted. Slate, slightly tinged with carbonat of copper, is to be seen amongst the rubbish: whence it is probable that copper ore was found along with the lead.
At Breda-head is a copper mine, chiefly of the sulphuret of copper. The miners being engaged in the more profitable employment of the herring fishery, I was unable to pay-it my intended visit; as the way down the cliff to the entrance of the level is considered difficult and dangerous, and no one was willing to accompany me.
Between Castletown and St. John's, and within about two miles of the latter place, are the mines of Foxdale, now drowned. These mines were said to afford a considerable quantity of fine lead glance; and, according to report, would have yielded much profit to the proprietors, had they been well managed. At present they are deserted. A large water-wheel, and the disjointed iron pipes, once used to drain them, lie scattered around. The rubbish from the shafts consists almost wholly of fragments of slate, mixed with pieces of brown blende, a little lead glance, and some sparry iron ore.
We find in the bottom of the valley, leading from St. John's to Peel, many marine exuviae. Tradition says, that the tide once flowed up this valley, nearly to the base of Mount Kreevey; a circumstance which the appearance of the country and the shells found in the alluvial soil, render highly probable; and which is further strengthened by:, the discovery of three iron anchors, at a great distance from the present shore, embedded in the same alluvial repository with the shells. The shells are neither petrified nor incorporated with consolidated materials, but simply embedded in the clay end sand of the soil. Here also have been discovered horns of animals, apparently of the stag kind, the largest of which measure nine feet from tip to tip.
A little nearer to Peel than St.John's, we meet with a loose sandy soil, resting on grey wacke slate. It stretches northward to Kirk Michael, forming a narrower of land, the higher parts being one hundred, or one hundred and fifty feet above the level of the sea, bounded on the left by the ocean, and on the right by land of somewhat greater elevation, which consists chiefly of grey wacke-slate sometimes covered by a bed of common clay. The sand is bounded on the south east by grey wacke-slate strata, which form the boundary of Peel valley in that direction. Peel castle stands on this rock.
The cliff at the northern part of Peel bay is a reddish brown sandstone, much charged with clay and iron. It sometimes contains fragments of quartz, and assumes the appearance of a breccia. The finest part is used for building, and a quarry is worked at this place a little above high water mark. The softer parts of the coarsest sort, where washed by the waves, have left several deep caverns and grotesque figures in the harder rock. The creeks along the shore exhibit the sand lying upon the slate in every variation of thickness: sometimes, for a short space, it disappears altogether. The sand-stone, being found immediately over slate, is to be regarded as sand-stone of the oldest formation, according to the Wernerian doctrine of the relative antiquity of strata. It corresponds exactly with Professor Jameson's description of the common red sand-stone of the Isle of Arran resting upon mica-slate.
At Kirk Michael the sandy soil expands over the whole northern part of the island in a line nearly west and east. Below this sand lies a bed of very pure common clay, called marl by the inhabitants. It generally lies at the depth of one, two, or three feet, still deeper as the ground is higher, and is very advantageously employed to give consistence to the light sandy soil. It is not from its containing lime that its utility does or could arise. Lime or even shell sand would here be prejudicial. The stimulating power of lime would exhaust such a soil as we now speak of. The chief desideratum is to give it sufficient consistence to retain moisture and to permit the plant to sustain its erect posture by means of its roots. It requires to be renewed every eight or nine years; and the ground bears plentifully, provided there is a proper rotation of green crops, barley, and oats. There is however a real clay-marl found near Ramsey, which contains a considerable portion of lime, and effervesces with acids. It is dug up at the depth of about eighteen inches, midway between high and low water mark in Ramsey bay. This also is in particular situations used with advantage as a manure. The substratum of clay rests on grey wacke-slate, as appears at the cliffs where the rocks are visible.
In many parts of this flat district peat is found in considerable quantities, usually from six to eight feet thick, and sometimes much more. It rests upon clay, frequently much mixed with sand. Trunks of the pine and of the oak are often observable. The former is accounted the most common, but I saw only the latter. It is black, very hard, quite free from decay, and is sometimes used by cabinet makers. The two sorts of tree are rarely or never found together; the trunks of oak lie in clusters: hence an opinion has been formed that the fir was indigenous to the country, and that the oak, the favourite of the Druids, was brought hither either by such of them as were fortunate enough to escape the retaliating punishment of the army of Suetonius, or by those who fled from Anglesey when that country was finally conquered by Agricola. To have levelled these trees with the ground must have required a considerable convulsion of nature; and if they existed alive till the extermination of the Druids from Wales, it seems probable that we should have some tradition of their destruction.
Near Ballaugh, and half a mile from Deemster Cullin's, upon an eminence, are about ten masses of sienite, three or four feet every way, forming somewhat of a circle.
At Ramsey the slate again commences, and continues to form the coast and country backward to the chain of mountains, almost to Derbyhaven.
Half way between Ramsey and-Laxey is said to be found, in a very small vein, a loose friable earth, of a greyish-black colour, softish to the touch, and used by the inhabitants for the cleaning of plate and other purposes. The specimen in my possession was procured from a Laxey miner, whose property it is by gift of the Duke of Athol. It does not effervesce, nor is it very soluble in mineral acids. It probably arises from a partial decomposition of slate.
The neighbourhood of Laxey is chief interesting-on account of its mines. These are situated on the banks of Laxey river, about one mile above that village. They are worked by two levels driven from the steep barks of the river. The upper level was begun about thirty years ago, but has not been regularly worked, and is partly filled up with water. It runs to the depth of about one hundred yards, following a vein nearly four feet wide, dipping to the east upwards of one foot in six. The vein consists of quartz, common brown blende, lead glance or galena, and occasionally some copper-green or carbonat of copper. Of the metallic matters the blende is the most abundant, next the lead, and lastly the copper ore. The height of the excavation is from four to fifteen feet, according to the extent or goodness of the ore. Interspersed with the lead glance, a small quantity of phosphat and a very little carbonat of lead have been found, but not in such quantity as to affect the smelting of the more profitable lead ore. For a considerable period the copper ore was disregarded, and thrown away among the rubbish. Some time ago the miners requested and obtained it of the proprietors What they collected was sold at the rate of 231. 14s. 6d. per ton, a price which shows that it was not a very pure copper ore. The blende here, as at other mines, was till within these few years thrown away, but is now sold at the rate of seven pounds per ton. This substance, till lately considered of no value, is at present used to glaze the coarser kinds of earthenware, The lead glance of this mine is very rich in silver, one ton of it affording, on assay, one hundred and eighty ounces of silver, or about 1/199 part, according to the report of those employed in the works. This lead ore is therefore the great object of the miner's research. It is common foliated lead glance with a pretty fresh lead-grey colour and strong metallic lustre. It is said that the other lead ores of this island never yielded above, and rarely so much as, seven ounces per ton. Where the copper ore appears in the vein the lead is in small quantity, and even that quantity is poor, being what the miners call burnt. There is a little sulphuret of iron, in the form of a grey powder found in this mine, which is separated from the other ores as it would otherwise render them slaggy and impede their smelting
The new level, which is now carried on, is situated about a quarter of a mile further down the river. It is twenty-eight yards below the level of the old excavation. One purpose of it is to drain the old level of its water. When I was there, in the autumn of 1808, it extended about two hundred yards; and three miners were at work upon it. The only Metallic substances yet found are carbonat of copper and blends. Its produce hitherto has not been sufficient to pay the expense of working, but the copper ore improves as they proceed.
Thie rock which the vein traverses is clay. date, of a great degree of hardness, and somewhat resembles whet-slate in its fracture, which approches to splintery in the small. It is blasted in the common way. From the frequent accidents that happen in the usual mode of blasting rocks, it would certainly be proper to try the more safe, simple, and expeditious method of covering the cartridge with sand, instead of hammering down fragments of stone to fill up the hole. This method was fully detailed in Nicholson's Journal, about three or four years ago.
All mines belong by prerogative to the Lord proprietor of the soil. They are let by him to one company of nine or ten persons, himself being one of these; and he clairms, as lessor, one eighth part of their gross produce.
The inclination of the slate increases as we go from Laxey towards Douglas, and it contains more veins of quartz. The general inclination of the strata near Laxey is about 45° but at Clay head it is from 70° to 75°,
Some of the slate strata are easily split into thin laminae, well adapted for the roofs of houses, while others, composed of thicker laminate, are well adapted for the walls,
About Clay-head and at various other places the clay slate is often so hard as to have given plentiful sparks of fire as I broke it with my steel hammer. Sometimes I founts it in detached masses; sometimes, forming a bed Several inches thick, inclosed on each side by the softer slate-rock, here and there firmly adhering to it as a part of the same stone, but more often easily detached. It is not divisible into thin laminae,. It occasionally contains small cubic crystals of iron pyrites. At the quartz vein, are less numerous, the slate is softer and more readily splits into thin laminae. It is usually hardest neat the veins. The slate not infrequently breaks into rhomboidal fragments, the consequence of its having a double cleavage. These strata form cliffs along the shore from one to two hundred and fifty feet perpendicular, till they are terminated by the sand of Douglas bay, which, near Douglas, stretches one or two hundred yards up the country. The upper strata are friable from decomposition, and have externally a light iron-brown colour, but internally are bluish-grey.
A little to the northward of Douglas is a bed of clay which has lately been used to form bricks, but they are of a very bad quality. Perhaps the clay found in the northern part of the island would afford a much better kind of brick; but the expense of coal is a great objection; and the abundance of stone, fit for building, renders this manufacture of less importance.
The pier of Douglas harbour is built of yellowish sand-stone: this is not a production of the island; but was imported from the vicinity of Runcorn in Cheshire. Mona castle is built of a very fine, white, and hard sand-stone. This was brought from the Isle of Arran.
From the facts above stated, it appears that the Isle of Man consists of primitive clay-slate and mica-slate, probably resting upon granite; of grey wacke-slate, and of lime-stone, which seems to belong to the rocks of transition, or. those which, in the Wernerian geognosy, are supposed to hold an intermediate place between primitive and floetz rocks; of sand-stone of the earliest formation; and of sand resting upon clay.
1 Alterum (latus Britanniae) vergit
ad Hispaniam atque occidentem solem: qua ex parse est Hibernia,
dimidio minor, ut estimatur, quam Britannia: sed pari spatio
transmissus, atque ex Gallia est in Britanniam. In hoc medio cursu
est insula quae appellatur Mona: complures praeterea minore. objectm
Caesar, de Bello Gallico, Lib. 5, Cap. 13.
2 Inter Hyberniam acBritanniam' Mona, Monapia, Ricnea, Vectis, Silimnus, Andros. Plin. Libel 4. Cap. 16.
3 i. e. head or hill of the bridge.