[From Lamplugh, Geology of IoM, 1903]
As stated in the introductory notes to this chapter, these mines are probably the most ancient in the Island, and were worked at a period anterior to the oldest records. They seem always to have been carried on fitfully and with long intervals of quiescence, just as during the 19th century. Copper and argentiferous galena have been the principal ores obtained, the latter especially in the northern part of the lode. Permission was asked in 18581 to raise iron-pyrites from the mine, but Sir W. W. Smyth have the opinion in his report for that year that the mineral was not likely to occur in quantity.
Cumming remarks that these mines " seem to have ' been wrought to some extent at the beginning of the seventeenth century, but have latterly been almost abandoned."2 Chaloner, in 1656, after mentioning the occurrence, of lead-ore containing silver at this place, adds3:-" The Veins of this Mine, by it's brightnesse, may plainly be discerned in the Rock towards the Sea; but it seemeth not possible to be wrought, in regard the Sea beats upon it constantly at High-water, unlesse it may be done by Mining within the Land ; a tryal whereof were worth the undertaking, in regard of the great benefit that possibly may ensue thereof." Feltham in 1798 (" Tour," etc.5 op. cit., p. 213) mentions that the mines though closed at the time of his visit, were worked and the ore brought from the shore in boats, and then carted to the smelting house at Port-le-Mary. Woods, Berger and Macculloch, early in the past century, found them standing idle, the last-mentioned author stating (in 1819) that they had been abandoned "twenty years ago." A plan of the workings1, dated 1826, is preserved in the Office of Woods and Forests.
Work was resumed soon after Cumming wrote, as there is a return of 25 tons of lead ore from them in 1850; and similar small quantities are recorded intermittently between this date and 1863, the returns for the whole period, showing 178 tons lead ore and 146 tons copper ore. The "South Manx Mining Company" which had been prosecuting the work seems then to have come to an end; but between 1866 and 1875 the "Bradda Mining Company" resumed operations, with a total output, as shown by returns between 1869 and 1874, of 364 tons lead ore and 193 tons copper ore. In 1881 the mine passed into other hands, and a new "Bradda Mining Company, Limited," was instituted, which ceased working in 1884. The returns of this company (18811883) give a total of 478 tons copper ore. The output from these mines seems never to have approximately reached the cost of production.
The lode, as already mentioned, is very conspicuous in the cliff on both sides of Bradda Head. On the south it occurs as a nearly vertical rib of white quartz and fault-breccia 30 to 50 feet wide, with well-defined walls, rising over 120 feet up in the cliff. It strikes N. 5° E. across the headland for 700 yards and reappears on the coast opposite Creg Harlot (six-inch map, Sh. 15), forming in places the face of the high cliff until truncated by a sharp curve in the coast-line. It is to these sections that Sir W. W. Smyth referred in describing the Bradda Lode as " the noblest surface exhibition of a mineral vein to be seen in Europe." 2
At its southern extremity the underlie of the vein is eastward at about 10° from the vertical. The quartz is full of cavities or vughs, and the metalliferous contents are distributed irregularly in detached strings and patches. I am informed that at South Bradda the lode was found to pinch rapidly in the workings below sea level, and that in the deepest part crushed slate rather than quartz was its chief constituent. The fissure appears to mark a fault cutting off the eastward prolongation of the flaggy grits of the headland; but the extremely contorted arrangement of the rocks in this vicinity hides the true relations of the strata. It is important to note that the vein, like most of the metalliferous lodes of the Island, lies close to the main structural axis of the slates (see p. 30).
At its northern outcrop the fissure is less sharply defined, and appears to have split into two or more branches with shattered rock between them, the western branch being distinguished as the Bulwark Lode. In this part of its course a small dyke of (Tertiary?) olivine-dolerite, 1 to 2 feet wide, is seen in the cliff to run along the lode, thus furnishing an especially interesting example of the association of the dykes of this type with the metalliferous deposits. In this case it is evident that the vein was in existence prior to the intrusion of the igneous rock; and no distinct indication is forthcoming to show whether the dyke has been the means of introducing or concentrating the ores in the fissure, as is suggested in some other instances (p. 488). The dyke is probably an offshoot from a broader intrusion visible at low tide on the shore 220 yards S. of Creg Harlot, which strikes away from the lode in the usual direction of the olivinedolerite group, viz.W. 35° N. Apparently while the main part of the dyke has held to its original course, it has thrown off a branch northward on intersecting the lode. On the opposite or eastward side, the course of the main dyke is indicated by a small outcrop at the side of a fence 250 yards inland, in the same line of strike. The intrusion was seen ia the North Bradda mine-workings by Sir W. W. Smyth, who in his report for 1873, after describing the 70-fathom level north of the shaft as being in a cavernous quartz lode with very little appearance of copper, remarks : " the south driving of the same level has been strangely interfered with by trap dykes, which in some places appear to border, but in others cut right across the lode, filling up a great portion of the space between the walls."
The workings on the vein are in three separate groups :the South Bradda Mine, at the foot of the cliff at the southern outcrop; the North Bradda Mine, in a similar position at its northern extremity; and a set of workings at a higher level, on the top of the headland about half-way between, which connect with an adit-level driven in from the cliff.
At South Bradda the older workings were carried on by means of an adit about half-way up the cliff, driven northward along the lode and connected with shafts from the surface of the headland and with sinkings where the ground was productive. The largest patches of ore seem to have been found in this locality. The later operations include a level over 100 fathoms long, driven upon the lode at a little above high-tide, with a rise connecting with the higher workings; and a shaft sunk from the base of the cliff to a depth of 30 fathoms, with a level along the vein at 20 fathoms, which disclosed nothing of importance.
At North Bradda there is, similarly, a series of old galleries in the face of the cliff; with newer workings descending below sea-level. The shaft at the base of the precipice is stated to have been carried to a depth of 72 fms. with levels at 27, 40, 50, 60 and 72 fathoms, mostly driven northward on the lode. The longest of these levels was the 60 fathom, which appears to have been carried 70 to 80 fathoms N. of the shaft, with poor results. Some ore was won in the 40 and 50 fathom levels, and a little lead in the 72.fathom S. The mine made 200 gallons per minute of salt-water. One of the higher galleries of this mine was driven south to connect with the Spittals Shaft, which was sunk from the upper surface of the headland. The plan of the mine prepared by J. A. Twigg of Chesterfield in 1826, now preserved in the Office of Woods and Forests, shows a through communication between North and South Bradda by an adit a little above sea-level, but this connection is not shown on the later plans to which I have had access. The workings above sea-level were the most productive of the mine both in the cliff and on the top of the headland; and Smyth notes (in his report for 1873), "It is a matter of reasonable disappointment that this great lode both here [North Bradda] and in the southern workings at Spitals Shaft has manifestly deteriorated in depth." The width of the lode in the upper part of the mine was in places between 10 and 11 fathoms. TIme vein was everywhere streaky, and without continuous ore bodies. A little native copper (moss-copper) is reported to have occurred in the parts of the mines highest above sea-level. The following minerals from the lode are recorded by Sir W. W. Smyth :-Malachite; Cuprite ("in minute octahedral crystals at the 40 fathom level"); Melaconite; Copper Pyrites; Copper Sulphate (old workings); Atacamite (" copper-ore changed under action of the sea-waterOld Mine, North Bradda"): Galena (argentiferous); Cerussite; Marcasite; Chlorite (" with quartz"); Agate (" parts of the vein-quartz in the Bulwark lode, North Bradda"); Hydrated Oxides of Iron (Ochre and Umber; "sometimes as gossan of lodes as at Ballacorkish and Bradda "
As the workings are now inaccessible, special value attaches to Sir W. W. Smyths descriptive reports, from which, in addition to the passages already quoted, the following details respecting the character of the lode have been culled. In 1858, Smythi mentions that at North Bradda "the eastern part of this huge lode presents a rib, between 2 and 3 feet wide, of softer charaeter, which was largely worked for lead ore under the Duke of Athol, and a little is still obtainable in the backs." In 1859, the workings at South Bradda are described, where the adit had been cleared, the lode cross-cut and a 20 fathom level driven some distance below the adit, "but although copper-pyrites, galena, iron-pyrites, and carbonate of iron are all there, they are in too small quantity to be of any value." itt is also mentioned that three shallow shafts opened on the hill above, and levels driven or re-opened there, had discovered large workings of the old men, but very little ore. In 1860, "from North Bradda, at last, some ore has been raised and sold," a very fair course of lead ore having been found in a winze down about 14 fathoms on the eastern lode. In 1868, we learn, "the Bulwark lode or farthest point W., under the sea, has so far been a disappointment, containing little else than quartz with an agate-like structure." In 1871, the North Bradda shaft was down 9 feet below 70 fathoms, and "here the lode is a great quartzose cellular mass of the hardest character, streaming on all sides with salt water, and containing only small spots of copper ore." In 1872, the workings at Spittals Shaft are described as being 25 fathoms below the adit from the cliff, which reached the shaft at 54 fathoms from the surface, the lode keeping its great size here "in all 50 or 60 feet wide, inclusive of the douk or soft argillaceous lode, and the Bulwark or western quartzose part," but copper ore occurred only in spots. On the last re-working of North Bradda, it is noted in the report for 1883 that the 40 fathom level, driven 50 to 60 fathoms N. of the shaft, had ore said to run 3 or 4 tons per fathom, but "a cross-course had disordered the lode in the end."
1 Of doubtful value; probably incorrect,
2 Bevans "British Manufacturing Industries," 2nd ed., p. 15. (London.1878.)
1 For the above details I amchiefly indebted to Messrs. H. Barkell.,J. Kewley, and W. H. Rowe.
2 See "List," in Transactions I. of Man Nat. list. and Antiq. Soc., vol. i., pp. 143-7.
If the Bradda Lode be continuous southward in the same line of strike, it should be again intercepted by the coast about ½ mile S. of Port Erin Bay; and we find in this locality a comparatively small but well-marked vein, with an easterly underlie, in the recess of Bay Fine, consisting of quartz and fault-breccia with iron pyrites. The strike of this vein, however, is N. 10 W., which is somewhat to the seaward of Bradda Head; it may possibly be a branch of the main fissure. At Aldrick, a similar recess ½ mile farther south, another fracture is revealed, striking about N. 30 W. and hading eastward, which emerges again on the shores of Calf Sound near Carrick Nay (six-inch, Sh. 18) 500 yards farther south, where it forms a broad lode. This has been tested by an adit reported to be 15 to 20 fathoms in length, from which a little copper-ore was obtained. I was informed by a miner who had worked both here and at Bradda that this lode resembled exactly the Bradda vein, of which it is regarded as the prolongation. If the identification be correct, the Bradda vein must have been shifted for 600 or 700 yards to the westward of its strike, either by a change of direction or by cross faulting. It is more probable however that, as at Ballacorkish, the ground is gashed by a set of approximately parallel but discontinuous fissures. There are no doubt later east and west faults here, as in other localities; but it is scarcely likely that these are large enough to carry the Bradda vein to Aldrick.
Though not permanently profitable, these mines have made a considerable output of lead and zinc ore, of which they are the only workings in the south of the Island to yield an appreciable quantity. Their early history is obscure, but the vein appears to have been worked and abandoned prior to 1811.2 It is also mentioned by Macculloch in 1819 as an abandoned working.3 The mines lie in the Manx Slates, about half a mile W. of the village of Colby in the parish of Arbory, on the lower slopes of a spur from the hilly axis of the Island. Work was resumed about 1862 and carried on more or less intermnittently at the one or other of two shafts until 1893, latterly under the title of the Rushen Mines. The aggregate returns, as given in"Mineral Statistics" between 1864 and 1894, show a total output of 3,693 tons lead ore, 2,869 tons zinc ore, and 138 tons copper ore.
The mines comprise two separate workings, not connected underground, the main shafts of which are about 000 yards apart. These workings appear to be on different lodes, or otherwise upon a lode which has suffered considerable lateral displacement. The lode or lodes have a general northerly strike, but while in the South or Ballacorkish mine the average direction is 2° to 5° W. of N., in the North or Rushen Mine it is about 10° E. of N. The hade or underlie is in both cases principally westward, at from 100 to 200 from the vertical, but with local deviations bringing it over in one part of the mines to the opposite quarter.
The South Shaft has been sunk to a depth of 75 fathoms, with levels at 12, 24, 36, 60, and 75 fathoms. The longest level is the 60 fathom, which has been driven about 490 yards north and 130 yards S. of the shaft. The North or Phosphate Shaft had a depth at the time of my visit in 1893 of 60 fathoms, with levels at 15, 30, 45, and 60 fathoms, of which the 45 fathoms went 60 yards S. and 260 yards N., and the 60 fathoms about the same distance N, these being the pioneer levels of the mine. In the uppermost part of the mines a ltttle copper ore was obtained, while the lower levels yielded only galena and zinc-blende, the latter chiefly on the western side of the lode. The ores were bunchy and irregular in their mnode of occurrence throughout. In describing the uppermost level in the S. shaft in his report for 1869, Sir W. W. Smyth remarks "in the best part of this the lode was as much as 5 or 6 feet wide, with more massive ribs of ore than were anywhere to be seen in the Island except only Foxdale and Laxey."
The galena of the south mine was richer in silver than that of the north, the former being stated to run 15 to 16 ounces to the ton and the latter only 3 or 4 ounces. The water percolating along the lode and pumped from the shafts averaged from 30 to 35 gallons per minute for each mine.
Besides the ores mentioned above, the following minerals are quoted in Sir W. W. Smyths list as occurring in the vein :Pyromorphite [phosphate of lead, from which the N. shaft derived its name], Cerussite, Chlorite (" according to Captain Barkell"), and Ochre and Umber [decomposed dolerite I]. The country-rock chiefly consists of rather flaggy slate; thinly bedded grits with slate partings were revealed in a short cross-cut E. in one of the lower levels.
The main geological interest of the mine lies in the relation of the lode to a dyke of olivine-dolerite, and in the cross-faults by which the metalliferous vein is thrown. The olivine-dolerite is apparently one of the Tertiary dykes (see p. 327) which diverges from its W.N.W. course on encountering the lode and follows it for a short distance. It is probably identical with the intrusion revealed in the bed of the Colby River a few yards below the corn mill, and again in the little glen 400 yards W. of Colby under the garden of Ballasherlocke (see p. 185).
As previously stated, the relations of the metallic infllhng of this lode to the intrusive rock afford important evidence as to the age of the ore-deposits, a study of the facts leading to the conclusion that although the lode existed as a rock-fracture previous to the intrusion, some part if not all of its metallic contents were. subsequently accumulated, therefore attaining their present position at comparatively late geological period (p. 489).
1 Unless otherwise indicated, the account of this
mine is based on my personal examination of the plans and part of the
workings, supplemnented by information supplied by Mr. F. Kitto, the
manager of the mine.
2 G. Woods, "An Account," etc., op. cit., p. 12.
3 "Western Isles vol. ii., p. 574.
Trans. Isle of Man Nat. Hist, and Antiq. Soc., vol. i., pp. 143-7.
SOUTH MINE.The dyke was first reached in the northward drivings of the South Mine within about 200 yards of the shaft and was more or less continuous thence to the end of the levels, accompanying and forming part of the lode, the ore lying sometimes to the east, but oftener to the west of it.
This portion of the mine was inaccessible at the time of my survey, but is described, with especial reference to the intrusion, in Sir W. W. Smyths official reports. The presence of the dyke is first mentioned in his report for 1870 1; in the following year Smyth notes the adit being stopped "on account of the apparent destruction of the lode by green stone" and in 1878, that in a deeper level the "black-rock or dolerite" made its appearance and seemed to militate against the productiveness of the vein. In 1879, he compares the intrusion to the [Carboniferous] igneous rock of Scarlet Point [from which it is, however, distinct, see p. 325] and describes its occurrence in the 60-fathom north level, at that time 210 fathoms out from the South Shaft, as follows :" I regret to add that the dolerite or black igneous rock . . . . has for the last 35 fathoms completely over powered the lode so that in the latter part hardly a trace of it is seen. Before that, it had accompanied the lode in a narrow band of 6 inches, which had appeared to do its productive qualities no harm There are hitherto but few precedents to go upon with reference to this dolerite and basaltic rook, but it is evident it is a question of much importance in this part of the Island from its action here, as well as at Central Foxdale, and in a minor degree at Bradda." In 1880, in describing the further progress of this level, he mentions that the lode was a mere string, not yet out of dolerite in which it has "been encased for 80 fathoms length,"thus distinctly implying that the lode proper is newer than the intrusion.
NORTH MINE.In the North Mine, where it was practicable in 1893 to examine the intrusion in the lower levels, I found the principal dyke to have a thickness of from 6 to 12 feet. Small fliers of the same rock occurred among the lode-stuff and were themselves sometimes dappled with lead-ore throughout, this association suggesting that part, at least, of the metalliferous contents of the vein had been introduced along with or later than the dolerite. In his earlier reports quoted above, Sir W. W. Smyth evidently inclined on the whole to the miners opinion that time lode was intruded upon and cut out by the dolerite but with the progress of the workings in the North Mine, and influenced, no doubt, also by evidence obtained about this time at Central Foxdale (p. 515) and Langness (p. 538), he abandoned this opinion; and in 1883 in describing the 30 fathom level of the new shaft he remarks that the ground was strongly invaded by dykes of dolerite, "the supposed prejudicial effect of which on the lode is, I think, not confirmed at this place, since there are parts in which a rib of this rock from 4 to 8 inches thick was flanked on either side by a branch of lode with lead and zinc ore."
We learn from the report for 1881 that in the upper level the lode was 4 to 8 feet wide, "having in places very beautiful examples of gossany lead-ore with white and green lead-ore;" and in 1883, that in the 30 fathoms the lode was difficult of definition, in places 14 feet wide, and two levels on it, though the branch usually opened on was about 2- feet wide, mostly occupied by soft gossan with abundant minute crystals of white lead ore.
From information obtained at the mine, it appears that in these workings the dolerite was continuous southward to the end of the longest driving, 60 yards S. of the shaft; while northward it was lost, at about 90 yards from the shaft in the 45 fathom level; at 95 yards in the 60 fathom level; and at about 100 yards in the 75or lowest gallery, probably striking off westward upon leaving the lode, with the same course that it held before intercepting the fissure, as it was not touched in the east and west cross-cuts made farther north. The dyke as dislurLed and shattered in places, probably by transverse movements after its consolidation, it is not clear whether the intru:ion is continuous from the South to the North mine, or whether we are dealing with separate and parallel branches. The end of the most northerly driving from the South Shaft lies about 240 yards east of the end of the most southerly driving from the North Shaft, and the character of the intermediate ground s unknown. It seems most probable that the lodes constitute a group of roughly parallel discontinuous N.-S. fissures, and that the intrusion in traversing the tract from east to west broke across from one to the other, and followed each in turn for a short distance only. The greater portion of the metalliferous deposits appear to have been afterwards concentrated in the fissures around and a little beyond the places at which the dolerite crosses them.
In the South Mine two large transverse east and west displacements of the vein have been recognised by the miners. One of these, known as the Dowk Lode, consists of a belt of crushed soft ground 66 feet broad, which sets in 15 yards north of the shaft and is said to shift the metalliferous vein 190 feet westward. The second, named King Slide, occurs 130 yards north of the shaft, and is supposed to displace the lode westward on the southern side. The miners identification of their lode beyond these breaks is of course open to doubt, and Sir W. W. Smyth refers to the workings north of the Slide, in his report for 1875, as on "a new north and south lode at about 24 fathoms beyond the old one," and in 1880 mentions the "Blende lode," 52 fathoms east from the main lode. In Great Laxey and other Manx mines working north and south lodes, though east and west displacements, reeognisable as normal faults, are not uncommon, they are never of this magnitude (p. 487).
1 MSS. in the Woods and Forests Office.
The site of this extensive but unproductive trial is on the eastern bank of the little glen ½ mile west of Colby (bh. 16), 760 yards north of the main road to Port Erin, and about 700 yards east of the Phosphate Shaft of the Ballacorkish Mine. The work seems at first to have been carried on in connection with the trial in the cliff at The Shock (p. 536) 2 miles farther north, under the designation of the "BELLABBEY AND FALCON CLIFF MINEs." The earlier workings appear to have been the adit levels in the glen north of Bellabbey. These were referred to in Smyths official reports for 1862 and 1869; we learn from the same source in 1870 that the adit level had been driven 87 fathoms and discovered only a string of mixed lead ore and blende 2 to 6 inches wide and a few yards in length. A shaft, ultimately attaining (in 1876) the depth of 72 fathoms, was then sunk and levels driven, mostly northward, from it at 12, 24, 36, 48, 60, and 72 fathoms, the longest being the 60 fathom which went 140 fathoms. Besides the ore in the day level above described, a little galena was found in the 36 fathom level north and in a few other places, but nowhere in profitable quantity. The supposed lode ran approximately north and south, with easterly underlie, and consisted of quartz (gossany at the top), crush-rock and dowk. Water was raised from the mine by the pumps at the rate of 100 gallons per minute.2 In Smyths report for 1872, when the shaft was down 31 fathoms, it is stated that the driving had "met with a little copper pyrites and zinc blende, but scarcely any lead ore." In his report for 1876 there is the following passage :" A very curious and exceptional little deposit of copper ore occurred in a warp or loop of the vein in the 48 level north 60 fathoms from shaft; a bunch, only a few feet in length, and, as I fear, only some 9 fathoms in height, but reaching at its best 12 or 14 inches in thickness, assaying 13½ per cent." It is also mentioned in this report that a cross-cut at the 72 level 9½ fathoms beyond the old lode had cut another lode also dipping east but at a steeper angle. In 1880, Smyth described a cross-cut at 60 fathoms going out west for 58 fathoms without attaining any results. This appears to have been the last work done in the mine.
1 These displacements have been indicated on the
published geological map, but much exaggerated owing to the small
scale of the map.
2 For most of these details we are indebted to Mr. R. Barkell, the late manager of the mine.
3 MSS. in Woods and Forests Office.
This consisted of a level driven into the face of the high precipitous cliff nearly opposite The Stacks, about a mile N. of Fleshwick (near I Slogh, of six-inch map Sh. 12). The country-rock is banded slate, and many dykes of microgranite of the Foxdale type, of greenstone, and of ohvine-dolerite, are exposed in the immediate vicinity (see p.p. 150-1). The lode consists of fault-breccia which is said to have contained a little lead-ore at the mouth of the level but none farther in. Its direction is slightly N. of E. at the entrance of the adit, but is reported to have changed to S. of E. inside. The trial was made between 1860 and 1870. Sir W. W. Smyths report for 1866 contains the following comment on it :" A fair amount of work done in the past year has only made appearances worse than before."
In " Mineral Statistics "the Bellabbey and Falcon Cliff Mines are credited with returns in 1872 and 1876-8, amounting in the aggregate to 59½ tons copper ore, 22 tons 17 cwt. lead ore, and 16 tons 8 cwt. zinc ore.
This name was applied to a small trial-shaft which was sunk, about the middle of last century, to a depth of 10 or 15 fathoms on the E. bank of a rivulet ½ mile E. of Colby and 300 yards N. of the highroad. No ore seems to have been found, but some of the weathered debris on the spoil-heap shows slight copper staining. The shaft has passed through a highly-sheared greenstone dyke curiously dappled with the green stain.
The site of this mine is in the north-western corner of Perwick Bay ½ mile S.W. of Port St. Mary, where the vein is intersected by the cliff in the recess known as Cotlooway (six inch, Sh. 15). The date of the first working is uncertain, but was probably before the end of the 18th century; Macculloch in 1819 mentioned the place (" Glensash, near Port la Marie ") as being at that time abandoned.3 Toward the middle of the past century operations were resumed, at first as part of the Bradda mining sett and afterwards as an independent company, but the mine did not at any time yield ore in paying quantity. The first workings consisted of an adit level driven into the cliff along the course of the lode, which runs N. 18~ to 20~ W. with an easterly underlie. Afterwards, a shaft was sunk from the surface 200 yards inland, which reached a depth of 50 fathoms, with drivings, chiefly southward under the sea, at 15, 23, 38 and 50 fathoms, Some small bunches of argentiferous galena of high quality, and kupfernickel (arsenide of nickel), are said to have been found in the sole of the day-level, this being the only known occurrence of the latter ore in the Island.4
From Sir W. W. Smyths official reports we learn that the mine was in operation in 1857 ; but working appears then to have been suspended until 1861 when the 15-fathom level was being driven north and south, exhibiting a little lead-ore in the latter direction; in 1862, the shaft had been sunk to 50 fathoms, and the "lode in the 38 fathoms [south] is of good size, but valueless"; in 1863, this level had cut a slide introducing water and a better-looking lode, 3 feet of which carried some steel-grained galena, while the 50-fathom level south showed nothing of promise. The report for 1865 records the collapse of the shaft "which had been put down among old workings, and appears to have been subjected to a sudden pressure by the fall of their walls." The accident brought the operations to a close, and the failure of the mine is locally held to have been due to this cause alone it is important therefore to note that Smyths report for the previous year (1864) contains the opinion that "this lode has always appeared to me a hopeless blank."
The Glenchass lode has been supposed to continue its course northward to the coast between Bradda Head and Fleshwick, where it has been sought for in some small trials in the vicinity of a branching dyke of olivinedolerite at Lhoob ny Charran (Sh. 15). An intermediate trial in the interior, close to the hamlet of Bradda West, known as the WEST BRADDA MINE, consists of an adit driven 24 fathoms, with a sump of 5 fathoms, on a lode striking somewhat west of north and hading east, which showed traces of blende and lead. In referring to this trial in his report for 1882,2 Smyth states that the lode had been tested by the old Foxdale Company 40 years previously, and expresses doubts whether it really coincides with that of Glenchass.
1 From information supplied by Mr.
3 "Western Isles," vol. ii., p. 575.
4 Recorded by Sir Warington W. Smyth in his "List of Manx Minerals" (Trans. I. of Man Nat. Hist. and Antiq. Soc., vol. i., p. 146), where it is stated that the ore was "found in small quantities about 1858 to 1862"; according to the same authority, Millerite (suiphide of nickel) occurred in delicate capillary crystal vein-stuff at a trial shaft at Rhenas, south of Kirk Michael" (see p. 547).
5 MSS. in Woods and Forests Office.
The occurrence of a little galena at this place is not only interesting as affording the only known locality3 for this ore in the Carboniferous Limestone of the Island, but also because the ore is associated, like the copper pyrites of Langness, with olivine-dolerite (Tertiary?) dykes. Cumming in 1845 described the circumstances as follows :-" This dyke has greatly altered the limestone, and more particularly in those places where it encloses a mass of limestone betwixt two of its branches. In this crystallised and altered limestone we meet with thin strings of galena."4 During the mining excitement in the Island some 20 years later, a small trial was begun at this place which was alluded to by Sir W. W. Smyth, inhis report for 1867 in the following terms :" At Castletown, a great cry has been made about a discovery of ore in the limestone rocks bordering the harbour. A shaft is now sinking, but in it I found no trace of vein, and it remains to be seen by driving a cross-cut from it whether anything be there on which a mine can be opened."
1 From information furnished by Mr. W. H.
2 MSS. in Woods and Forests Office.
3 There is a local belief that lead ore occurs also in the limestone at Balladoole, a little to the north of the foreshore ; but the evidence offered is unsatisfactory.
4 Quart. Journ. Geol. Soc., vol. ii., pp. 331-2.
5 MSS. in Woods and Forests Office.
The prolonged and expensive series of trials on the western shore of Langness on some small copper veins known to Cumming 1in 1845 seems to have been commenced about 1875, as we learn from Smyths report for that year 2 that "some strings and vein-like deposits of occasionally 2 or 3 feet in depth have been opened upon the foreshore and yielded some very good copper pyrites." The work was prosecuted at various spots from that tune until 1880 ; and after being at a standstill for a few years, was, towards the end of the decade, resumed near the southern extremity of the headland, but has since been again suspended. The strings of ore were first discovered in the Carboniferous Basement Conglomerate, but most of the workings have passed into the underlying slate. As at Ballacorkisli, North Bradda and Central Foxdale, the close association of the metalliferous deposit with intrusions of olivine-dolerite lends considerable geological interest to the matter. Unfortunately in spite of the heavy expenditure of capital the total quantity of ore yet obtained has been quite insignificantonly 10 tons 18 cwt. of copper pyrites standing to the credit of the mines in the official returns (" Mineral Statistics" for 1890 and 1892). The direction of the supposed lodes is approximately north and south, with an easterly dip. The strings of ore have been found alongside or in close proximity to small ohvinedolerite dykes that fill the fissures.
The most northerly working is a small trial-pit just above high-water mark on the foreshore of Castletown Bay 420 yards N. of Langness Farm; this has a depth of 26 feet, starting in Carboniferous Limestone, and ending in dark Basement Conglomerate.
The next is a shaft 320 yards S.W. of the above-mentioned farmstead, sunk to a depth of 12 fathoms, on the raised beach near high-water mark, the upper 50 feet being in conglomerate and the remainder in slate. From the bottom a cross-cut was driven westward under the shore, at first in slate but afterwards in conglomerate, and is described as follows in Sir W. W. Smyths report for 1876 :" This passes through mottled slaty rock beneath the Conglomerate and at thirty fathoms out has intersected the vein of 2 or 3 feet thick including a black stone or trap and with some good portions of yellow copper ore in it."
The most extensive trial of the series is situated on the top of a low cliff 225 yards farther south, where a shaft has been sunk vertically in slate to a depth of 44 fathoms, with drivings westward from it under the shore. The shaft is said to have interc~~pted the eastward dipping lode at 30 fathoms from the surface. The lower part of the mine was flooded .during my stay in the neighbourhood, but I was able in 1893 to examine a cross-cut to the lode at 12 fathoms depth, in which the junction of th~ slate and conglomerate was seen to occur at a small fault striking N. 8° E., and to be accompanied by a rib of intrusive dolerite like the branching dyke so beautifully exposed on the foreshore above (p. 195). Strings of copper pyrites lay along the junction of the dyke with the conglomerate, and to a minor extent at its junction with the slate. On the opposite side the ore in places permeated the margin of the igneous rock, like the lead-ore at Ballacorkish (p. 534), and was most plentiful in a bifurcation of the dyke.
The 40 fathom level was described by Sir W. W. Smyth in his report for 1878, as a cross-cut running S. of west for 35 fathoms in clay-slate, with short drivings along a string running N. and S. at 18 fathoms from the shaft and along a second a little farther out having a slightly different course, both utterly barren and devoid of promise, leading to the conclusion that the bunch or two of ore in the overlying conglomerate were extinouished at this depth in the slate.
The evidence on the foreshore shows that the relation of the dyke to the lode is the same here as at Ballacorkish and North Bradda, an intrusion striking W.N.W. across the headland (p. 177)having been diverted northward for a short space by the fissure, but soon escaping from it and going off W.N.W. again. The ore in places impregnates the matrix of the Qonglomerate as well as the dyke-rock, and must have been concentrated in its present position either during or after the intrusion. It is important to note that both here and at Langness Point the strings of ore occur only in the proximity of the dykes; at the same ti,ne, there are many more of these dolerite dykes in the neighbourhood which are not accompanied by mnetalliferous veins.
The course of the lode of the above mine after it is abandoned by the dyke is indistinct, and does not appear to give rise here to a displacement at the surface; though it mnay possibly be prolonged into the sharp anticline breaking northward into a small fault which brings up the oval inlier of conglomerate among the limestones on the foreshore N.W. of Langness Farm (p. 195).
Southward of the shaft, at a distance of 200 yards, an adit has been driven into the cliff through banded slates traversed by small sheared preCarboniferous dykes of greenstone; and 300 yards south of this again, just beyond The Arches (p. 190), there is another adit 36 fathoms long, in the Carboniferous Conglomerate.
The remaining workings are in slate at Langness Point, east of the boundamy of the Carboniferous rocks. Here, on the south shore of Port Bravag (6-inch, Sh. 19) 200 yards east of the extremity of the headland, a dyke of dolerite a foot or two wide, striking N. 8° to 15°E. along a fissure in slate, showed a string of copper pyrites along its western side. To test this, a shaft was sunk to 26½ fathoms on the ridge about 100 yards to the eastward, and a north-west cross-cut commenced to intercept the lode, but was not completed. Specks of galena were found on joint-faces in the slates of this level. A smaller pit was then sunk to 8 fathoms in close proximity to the fissure, and a short cross-cut driven from it to the dyke, but the result was discouraging. The present surface of the slate at this point is nearly identical with the ancient floor on which the Carboniferous Conglomerate originally rested (p. 191), so that the disappearance of the copper-ore downward in this place as well as in the previous workings suggests that these particular metalliferous strings tend to die out on passing down from the conglomerate into the slate-rocks.
The cliffs on the eastern side of Langness have been tested in several places by short excavations along planes of dislocation and crushing in the slate, but without revealing anything of promise.
1 Cumming says, "I may also mention that along the side of the dike cutting the
southern point of Langness, and ma narrow gully, I have met with fine veins of copper in the schist." Quart. Journ. Geol.
Soc., vol. ii.,p. 332.
2 MSS. in Woods and Forests Office.
3 Our thanks are due to the engineer and captain of the mine for facilities afforded on this and other occasions.