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BRITISH INDUSTRIES. No. IV. – Manufacture of British Serpentine.
To the home returning wanderer of the deep blue ocean, the ever welcome headland, the Lizard, is well known. Its two lights streaming far o’er the western waves, always offer a kindly welcome to the tempest tost and the stranger. To the tourist, however, this remarkable promontory, which
All arrow like in ocean’s breast”
is comparatively little known; yet, within the limits of a day’s ramble are to be found some of Nature’s wonders. The tourist seeking for the picturesque, will find coast scenery of unequalled beauty, and of singular wildness; the botanist will here discover plants indigenous, which are unknown in any other part of our island; here, in full perfection, he will find that graceful heath the Erica vagans – and on the Asparagus Island, in Kynance Cove, still flourishes the plant in its native wildness from which it derives its name. To the geologist and the mineralogist, the serpentine, the steatite, the diallage, together with the hornblende slate and rock, and numerous rare minerals of the Lizard district presents an interesting and important field. To the economist, the manufacture of serpentine rocks into numerous articles of use and ornament, with various other branches of industry, the wild region of England’s most southern point will not prove barren.
This district should be visited by whose who desire to know their native land. Cornwall has been placed by some recent writers as a place beyond civilisation, so suddenly have we brought ourselves to look upon railways as a necessity, and an iron road is not yet completed through Cornwall, although one is in the process of construction.
The traveller arriving at Plymouth by railway has then to make his choice between two fast mail coaches, one a stage coach, a four horsed omnibus, and a succession of steam vessels which pass between Plymouth and Falmouth at least four times during the week. The coaches pass through a varied, beautiful, and romantic country. At one time a richly cultivated agricultural country will be spread out around the tourist, with fine rivers winding amidst fertile hills, and in many places, assuming the aspect of lakes; then he will pass through deep valleys, the hills on either hand wooded from the base to the summit; the ‘land of brown heath and shaggy moor’ will next attract by its wildness – and here the evidences of ‘tin streaming’ and mining, with the characteristic scenes around the ‘China clay’ works, will at once show the peculiar industries of the county. Such scenes as these alternate, and after a pleasant ride of about eight hours’ duration, the town of Falmouth, with its noble roadstead and its fine but neglected harbour, forms a splendid finish to a peculiar, and in every respect interesting, panorama.
The sea voyage is made between Plymouth and Falmouth in about five or six hours. A fine iron bound coast is passed, and the well known headlands of the Rame Head and the Deadman, with the bay of Whitesand and of St. Austle :- and, away far amidst the waters of the English Channel, will be seen rising that splendid monument of a fine humanity and engineering skill – the Eddystone lighthouse.
“But,” says the reader, “we have only reached Falmouth, and where is the serpentine and the Lizard?”.
The land stretching far south, which is seen on entering Falmouth harbour, or that which is seen from the hills above the town, is the point hiding the Lizard from view – the dangerous reef of rocks known as the Manacles, near which so recently occurred the sad catastrophe of the ship ‘John’, with her unfortunate emigrants. From Falmouth a vehicle can be obtained with which the Lizard can be reached by either of two routes. By one, the Druidic rock of Constantine, called the Men, or Main rock, or the Tolmen may be seen. On the surface of this huge mass of granite are a number of remarkable hollows, or basins, which are regarded by antiquaries, as rock basins, at one time held sacred for Druidic rites. By the other route the town of Helston, formerly Ellas’ town, a name which appears to denote a Saxon origin, will be passed through.
Arriving at the Lizard Town, the tourist will find a respectable inn, and from it as a centre he must now pursue his researches.
There are but a few spots in which the serpentine formations are seen to more advantage than in the romantic Cove of Kynance. Passing over a barren moor, and advancing towards the sea, which appears spread out without a bound; dark rocks are eventually seen beyond the cliffs, and towering above them, remarkable for their sombre character, and their bold outlines, as seen with a sky only for a background. These are presently found to be insular groups of rock, a portion of the group known as the Asparagus Island, from the circumstance of that plant growing in considerable luxuriance upon them.
The disturbance which originally produced these beautiful rocks, has thus thrown them into a series of irregular undulations, and the access to Kynance Cove is down and along the hollow of one of the waves, forming rather a ravine than a valley, through which in the winter rushes a torment, which is, however, reduced to a small stream scarcely visible amidst the boulders crowded along its bed.
A large water wheel, at the bottom of the valley, forms an exceedingly picturesque object, and shows that some human industry is active, even in this retired spot.
This water wheel is employed to turn the rude machinery by which some works in the serpentine are effected, but these are on a small scale. The people occupying some small cottages employ themselves in collecting choice specimens of serpentine and steatite, forming them into pedestals, tazzi, candlesticks, brooches, bracelets, and numerous other ornamental articles, which are sold to the strangers who visit this remarkable spot.
If the visit is made at a time of low water, a series of wave worn arches and deep caverns can be inspected. The rocks all around, especially if still moist with the sea, shining brilliantly in their deep green colour, veined with the finest reds. The polished surface, and the rich colour of these cliffs of serpentine, give a peculiar beauty to the Cove of Kynance, such as will scarcely be again met with in this country; and in contrast with the pure white sand of the beach, and the remarkably transparent waters which lave it, it is singularly striking. Many great natural curiosities, amongst others, the Devil’s Bellows, and the Devil’s Mouth, will command the attention of the stranger; but we have not to deal with these on the present occasion. The serpentine formations of Cornwall are geologically not a little remarkable. At one or two spots in Cornwall besides the Lizard small patches of serpentine are found. At Clicker Tor, on the south of Liskeard, we find serpentine slates, and near Veryan it is associated with dillage rock. No connection can, however, be traced between those and the serpentine of the Lizard district. The best account of these rocks is found in Dr. Boase’s ‘Primary Geology’, to which we are mainly indebted for the following facts.
The serpentine of Cornwall is proved to be a compound of diallage and felspar or perhaps rather of compact felspar, with frequent transitions into diallage. The serpentine belongs to the magnesian rocks, which may be grouped into three genera – diallage rock or euphotide, serpentine, and talc schist. The euphotide consists of felspar and diallage, both of which are often very crystalline, and when so very distinct, putting on the forms of granite in which the crystals are aggregated together, and penetrate each other. The felspar of the serpentine, however, differs from the felspar of the granite in its containing magnesia. The serpentine rock exhibits a great many varieties, some of which are hard, whilst others are so soft as to yield to the nail. This difference appears to depend on the felspar base, which undergoes several modifications, between a crystalline compact and granular state, as seen in the precious steatitic, common, and ollareous serpentines, in the same manner as the rocks of the porphyritic group assume various aspects, according to the composition of the compact felspar base; with this difference, however, that in these, the proportion of the silica modifies the compound, whereas in serpentine the changes are attributable to the relative quantity of magnesia. The accessory mineral diallage, also imparts characters to the serpentine, according as it is intimately combined with the base, or is disposed of in distinct forms.
Sir Henry de la Beche in his ‘Geological Observer’ speaking of serpentine says “The position of the Lizard serpentine, and the diallage rock found with it, seems much the same with these minor portions of serpentine more eastward (at Clicker Tor and Veryan). It occupies a somewhat comparatively large area, reposing upon hornblende slates and rock, which appear little else than the ordinary volcanic ash beds. There is often an apparent passage from the diallage rocks into the serpentine, while also there seems an intrusion of serpentine amid the former, as between Dranna Point and Porthalla. Whatever the cause of this apparent passage may have been, it is very readily seen at Mullion Cove, at Pradanach Cove, at the coast west of the Lizard Town, and at several places on the east coast between Landewednach and Kennick Cove, more particularly under Balk, near Landewednach, and at the remarkable cavern and open cavity named the Frying Pan near Cadgwith. It is generally found that at this apparent passage of one rock into the other there is calcareous matter, and a tendency to a more red colour in the serpentine near its base than elsewhere”.
These conditions are shown in an interesting manner at the quarries and works of the Lizard Serpentine Company.
The chemical composition of these serpentine rocks varies considerably, but a careful chemical examination of some large pilasters of the serpentinous rock, in the Museum of Practical Geology, London proves it to be a mixture of silicate of magnesia and carbonate of lime, with minor quantities of oxide of iron, and alumina. Water is also a marked ingredient, and it must not be forgotten, in selecting serpentine for works of art, that some varieties are far more durable, containing less water than others. It may be instructive to state the differences in varieties of serpentinious rock.
Precious or Noble Serpentine is translucent and massive with a rich green colour of pale and dark shades. This occurs in Sweden, and some good specimens are obtained in the Isle of Man, and in Aberdeenshire. Its composition is
Common Serpentine, as found at the Lizard and other places, is found to be
Iron and Chromium 13.26
Picrolite is a fibrous variety of serpentine somewhat resembling asbestos, but of a dark green colour.
Marmolite is of a pale green colour, sometimes nearly white, and
Retinalite has a resinous appearance, a colour varying from honey yellow to oil green, and is translucent. Mr. T.S.Hunt, of the Canada Geological Survey, has analysed a greenish white sub translucent variety, in which occurs chromic iron ore; is afforded
Alumina and Iron 3.6
It will be seen, therefore, that serpentine is really a silicate of magnesia and water, the other constituents being unimportant, except the iron and chromium, to which it owes its colour.
It is only within the past few years that any manufacture of serpentine has been carried on in this country. At Loblitz, in Saxony, and in Franconia, several hundred persons have been for a long period engaged in working it. Until the Penzance Serpentine Company opened quarries at the Lizard, and established works at Penzance, but little had been done towards applying this material to either use or ornament. A few gentlemen resident in Cornwall had employed this beautiful material for ornamental purposes in their houses, but beyond this, the manufacture was confined to small ornaments which were sold at the Lizard to visitors.
The beautiful collection of specimens which were exhibited in Hyde Park, in 1851, by Mr. Organ, for the Penzance Company, and by Mr. Pearse of Truro, first called public attention to it. Since that time its manufacture has largely increased. The Penzance Company have erected extensive works, in which steam power is employed to turn and polish the serpentine stone; while the Lizard Serpentine Company have opened extensive quarries near Poltesco and fixed their works on the spot. As far back as 1839 the late Sir Henry de la Beche wrote as follows, amidst other passages on the economic geology of Cornwall –
“Much of the serpentine of the Lizard, though hitherto most strangely neglected, is extremely beautiful, particularly where veins of red traverse the olive green ground, mixed with lighter tints. This variety chiefly occurs in the lowest parts of the rock, adjoining the hornblende slate and rock, both of which may also be cut and polished to advantage. The best place for obtaining the red striped varieties which we have seen occur at the Balk, near Landewednach; at the Signal Staff Hill, near Cadgwith; at Kennack Cove; and on Goonhilly Downs, on the N.W. of Roscrowgie. A variety, with an olive green base, striped with greenish blue steatite veins, is found at the commencement of the serpentine near Trelowarren, close to the high road from Helstone to Goonhilly Downs. As to variety of tint it is almost endless. We must not, however, neglect to notice a very hard and beautiful variety, having a reddish base studded with crystals of diallage, which, when cut through and polished, shine beautifully of a metallic green tint, in the reddish base.”
All these varieties can be seen in the manufactured articles at the show rooms of the Lizard Serpentine Company, 20, Surrey Street, Strand, and at the works of the Penzance Company. The authority already quoted, in continuation of the above says:-
“It has been supposed that blocks of fair size could not be obtained from the Lizard serpentine. This we are inclined to consider a somewhat hasty opinion, inasmuch as quarries to ascertain the fact have not been opened in those places where the hard weathered fragments, chiefly now employed in the few ornamental works executed in this material, would lead us to suppose that the rock might be sufficiently solid beneath to afford serpentine in large solid blocks. It is to be regretted that such situations as the Cadgwith Signal Hill have not been fairly worked. Blocks of fair dimensions, from which chimney pieces have been cut, have already been obtained of the reddish brown serpentine containing crystals of disseminated diallage – a rock which occurs in large quantities near the Black Head on the east, and north west from Lizard Town on the west”.
The attention of architects and others has recently been much directed to the serpentine stone obtained from this district, and the public have now an opportunity of inspecting the manufactures produced during the present year by the Lizard Serpentine Company.
Although this stone has for many years past attracted occasional notice, it is but recently that commercial enterprise has been energetically directed to the development of the district in which it is principally found. The failure of many, indeed of all the attempts, formerly made to introduce the material into general use produced as a natural consequence a prejudice of which the result has been that an ornamental stone of very great elegance has been condemned as altogether useless, or adapted only for exceptional application. The brittleness and unsoundness of the stone found on the surface and the varying results of numerous chemical analyses such as we have given, induced geologists as well as practical men to conclude that these defects and a want of equal consolidation of component parts were inherent in the material. We have shown that the late Sir Henry de la Beche suggested that these disadvantages would in all probability be overcome if quarries were opened to some considerable depth, and stone obtained which had not like that hitherto manufactured been subject for ages to the influences of air and water.
The justice of this opinion has been fully proved, and the quarries of the Lizard Serpentine Company having during the last twelve months been opened by powerful Derrick cranes to a depth of from forty to fifty feet, and the super incumbent mass of loose and unsound stone having been thrown over the cliffs, the Company have come upon extensive beds of consolidated rock which are worked in the same manner as quarries of granite. The size of the blocks raised formerly varied from two to ten feet, but the masses have increased to so great an extent with the depth, that it is now frequently found necessary to break the blocks up before they can be removed. In proof of the greater consolidation of the material we are assured that this process of division is accomplished by ‘splitting and tearing’ in the same manner as in the case of granite, and there is now no difficulty in obtaining sound blocks of nine, ten, or twelve feet in length.
The same prejudice which led to many to form a hasty conclusion as to the want of size and soundness in the blocks to be obtained, also operated in condemning the stone in reference to its working capabilities.
The Lizard Serpentine Company, it appears, did not in the first instance intend to manufacture, but they found it necessary to change their plan in order to introduce the stone into general use, and they have erected a factory with powerful machinery in the immediate neighbourhood of their quarries.
The stone was formerly supposed to be not only brittle in the extreme, but equally hard with granite, and it was considered that the expense of manufacturing would far exceed that of working the marbles used in this country. Experience has again proved these forebodings to be incorrect. The stone obtained from the lower beds of the quarries loses its brittleness, and is found to be equal in its working quality to any of the coloured marbles so extensively manufactured. The process of sawing, manufacturing, and polishing are very nearly the same and the companies say they are not more expensive than in the case of marbles; but a little experience of the peculiarities of the stone is of course essential to success. The prices at which manufactured goods can be brought into the market are nearly on a par with the coloured marbles, to which in point of beauty and variety the stone is very far superior.
Architects have long been acquainted with the extreme beauty of the material. The Lizard serpentine is distinguished from that obtained in other parts of the world by the variety and vividness of its colours, and the interesting white lines caused by veins of steatite. This steatite or soapstone is a source of weakness, and although admired by many, should be avoided in chimney pieces, as on parting with its water, the veins of the steatite are liable to crack. The Lizard promontory is composed of serpentine, and in proof of the durability of the material, it is sufficient to refer to the circumstance of its having been placed by nature on so exposed a part of our coast, where it has resisted for ages the fury of the Atlantic Ocean. But although the serpentine formation is so extensive, the stone applicable for manufacture forms but a very small portion of the whole. The coloured and serviceable stone run in beds varying from four to forty feet in width, and the blocks are of the irregular form in which statuary marble is found.
The prevailing shades are red, black, green, white, and yellow, blended in endless combinations and varieties, and mingled with sparkling crystals of diallage. The red, unlike any similar shade found in other stone, is bright and blood like, sometimes giving the effect of a gem, and in all cases imparting a warmth of tone which cannot be obtained in any species of marble.
For chimney pieces and other works of domestic architecture, the serpentine possess a great recommendation in being proof against the action of the ordinary acids so prejudicial to marble. For church architecture it is peculiarly fitted, as possessing not only the warmth of tone above adverted to, but great elegance and lightness of appearance in some varieties, while others are distinguished by a grand and massive character. For ornamental application, it is also very well adapted, and the Penzance and Lizard Companies have already manufactured some magnificent vases and tazzas, in addition to chimney pieces, columns, and fonts. That the stone will now be brought into general use will not be doubted by any, after an inspection of the productions manufactured by these companies; which while they exhibit a marked improvement in the character of the material, are still distinguished by those peculiar beauties which have long been known to attach to the stone, but which it is difficult, if not impossible, to describe in adequate terms. The steatite which is found in connection with the serpentine was formerly used in porcelain manufacture, but we believe it is not now so employed; and the serpentine itself was once employed in the manufacture of magnesia and of Epsom salts; since it contains nearly forty per cent of this earth. The dolomite rarely containing so much as this, is extensively used at Newcastle for this purpose.