Chapter L: J. M. Daguerre, born 1787, died 1851 (6)

In chemical composition the diamond is pure carbon, one of the most commonly diffused of the elementary bodies, as it enters into the constitution of the atmosphere, of all organic bodies, and of a vast number of mineral substances. Carbon in a less pure form also occurs naturally as _graphite_, _plumbago_ or _black lead_, and in other conditions comes into ordinary use as already explained in our article on Iron. It was only towards the end of the eighteenth century that the composition of the diamond was demonstrated by the celebrated French chemist, Lavoisier, who actually burnt a diamond in oxygen gas, and found the resulting product to be carbonic acid gas, identical with that obtained by similarly burning a piece of charcoal. Soon afterwards another French chemist, Clouet, confirmed Lavoisier’s conclusion by producing _steel_ from pure iron and diamond heated together, an experiment of much significance when considered in the light of the remarkable relation between these substances, which is one of the latest discoveries of our century. It should be observed that Clouet’s result implies a fusion of the diamond as well as of the iron in the act of entering into chemical combination.

Like nearly every solid substance of definite chemical composition, this pure carbon takes the crystalline form. The phenomena of crystallization are of the highest interest and beauty, for in them we see shapeless matter fashioning itself into definite and often perfect geometrical solids, as if it had been wrought by the hand of some mathematical artist. Every substance forms crystals of some one shape when the conditions are identical, and one essential condition for any crystallization is that the particles should be capable of free movement in arranging themselves, and this condition can occur only when the substance is in the state of liquid or of gas. Crystals are commonly deposited from solutions when the solvent evaporates or is cooled down; or they are formed when a fused substance solidifies. In either case the crystals are the larger and more perfect as they are allowed the greater time to form. Now, carbon in any of its conditions has been found to be absolutely infusible and insoluble, and therefore the origin of the diamond has long been a puzzle to scientific men, very diverse surmises having been propounded on this subject. Some have thought it was separated from carbonic acid by the action of heat, or of electricity; others, that the carbon had been gasified by subterranean heat; others, among whom were Newton and the German chemist, Liebig, believed that heat had nothing to do with it, but that the crystals slowly separated from vegetable matters (hydro-carbons) in the process of decomposition under some unknown conditions; others, that the diamond crystallized out from liquid carbonic acid, holding under pressure some unknown form of carbon in solution; others, that carbon was ejected by volcanic action in a fused state; and so on. We hope to show that the problem has at length been solved, and how.

The shapes of the natural crystals of the diamond must not be confounded with those of the cut brilliants. The most frequently met with of the former is the octahedron, or eight-sided figure, such as would result from two square pyramids joined base to base, the triangles forming the sides of the pyramids being of such a height that the three pairs of opposite points are equidistant one from another, so that the octahedron enclosed in a cube would have an apex in the middle of each surface of the cube. There are other shapes of diamond crystals, but they are all related to the cube, that is, they are all obtainable from the cube by successively slicing off edges and angles. The natural diamond sometimes has as many as 48 faces formed by such a process. This will easily be understood by the reader if he will take a cube of common soap and perform on it these operations _gradually_ with a sharp knife, taking care always to make the new faces he produces equally inclined to the adjoining ones. He may begin by cutting off a tiny piece from one corner of the cube, forming a small equilateral triangle; then let him do the same at two opposite corners, and again at all the eight corners. Then he should make the cuts larger and larger, always producing equal sized equilateral triangles so long as these can be formed. In every case he will have shaped out such forms as belong to diamond crystals. Instead of this, he may pare off one or more edges of the cube, or he may in various ways combine the two operations, and he will probably be surprised at the variety of forms producible in this manner, all derived from the original cube and all representing possible forms of natural diamonds, and indeed those of any substance that crystallizes in the _cubical system_. A model of the diamond octahedron can be readily made from the description already given, and the whole series of operations will constitute an elementary but very instructive lesson in the science of crystallography.

Diamonds are liable to occur with every imaginable distortion, so as to be scarcely recognizable by their external form. A very pure smooth uncut diamond, belonging to the Rajah of Mattam in Borneo, is shaped exactly like a pear, two inches in length. By the way, battles have been fought for the possession of this gem, and it is said that,£200,000 was vainly offered for it. The diamond, notwithstanding its hardness, splits with comparative ease in certain planes, and by such cleavage (a property common to all crystals) the octahedral form commonly emerges. It was not until the middle of the fifteenth century that the art of cutting the diamond into regular facets was practised, and this can be done only by the aid of diamond powder, prepared by crushing fragments and faulty stones in a hard steel mortar. The first operation is to split the stone by its natural cleavage, and the rough facets so produced of two diamonds are ground together until they are quite smooth. The grinding of other facets and the polishing are effected on horizontal discs of steel making 2,000 revolutions per minute, and overspread with diamond powder mixed with olive oil.

The external surface of the diamond in its natural state is often very rough, the stone being always coated with a more or less opaque crust, so that its translucent interior is concealed or veiled; but when the reflection from its inner surfaces pierces this veil it glows as if lighted from within, giving that peculiar appearance which is called its “fire.” The surfaces of the diamond crystals are very often curved instead of being flat, and the dodecahedral shape, when this is the case, takes on an almost globular appearance. Diamonds of all colours are found, as well as the highly esteemed colourless stones. Yellow ones of various tints are frequent,—orange, brown, and pink are not very rare; but red, green, blue, and black are almost unique, at least in a condition to form large and perfect gems, and are accordingly much prized. The black diamonds found in Borneo are so hard that ordinary diamond powder has no effect whatever upon them; they have to be manipulated with their own dust. The nature of the substances that impart these colours to the diamond has never been made out; they must be excessively small in quantity. When a diamond is burnt in air or in oxygen gas by aid of a large burning glass or otherwise, an extremely minute quantity of ash remains, and this often retains the shape of the stone, in the form of a most delicate network; and of the composition of the ash, this much has been made out: it contains silica and _iron_. We shall find that the presence of the last named element, although but in the merest trace, is not without significance.

The purely utilitarian uses of the diamond are few, but of importance. The most familiar is in the glazier’s tool for cutting glass, and in connection with this we may mention a fact not generally known, namely, that though any point of a diamond will _scratch_ glass, it is only by a natural point of the crystal, and that point of a certain shape, that glass can be _cut_. Another kind of diamond, valueless as a gem, has been turned to good account in Major Beaumont’s invention, described in our section on Rock Drilling Machines, to which the reader is referred. Minute diamonds are employed for writing on glass, for very fine engraving, etc.

Having now said sufficient about diamonds in general to give the reader an interest in the subject, and yet but little more than was needed to impart the information necessary for following the further development of the theme, we approach the discoveries in this connection which have specially distinguished our century. We must transfer the reader’s attention to South Africa, and if he can refer to any recent map of that region, particularly to one showing its physical features, it will be of advantage.

In 1867 some children, playing near the banks of the Orange River, found what they thought to be merely a pebble prettier than the rest. A neighbour seeing the stone in the children’s possession, obtained it from their mother for a trifle. It passed through several hands, and was bought at last by the Governor of the colony for £500. The discovery shortly afterwards of other diamonds in the same locality attracted numbers of persons to the district, and especially to the banks of the Vaal River, which speedily became the scene of a great search for diamonds. Though this search was confined to merely the surface of the soil, it was attended with considerable success, and many fine diamonds rewarded the diligence of the eager seekers. One of the most remarkable stones for its great size, which equalled that of a walnut, was discovered by a Kaffir. When this gem had finally reached the hands of Messrs. Hunt and Roskell, of London, its value was estimated at no less than £25,000. News of these discoveries having spread, a rush set in for the diamond-fields of the Vaal River, and the banks of this stream soon presented an animated spectacle. Europeans flocked to the spot, London jewellers sent agents, and the inevitable Jews appeared on the scene to purchase the precious gems from the lucky finders. It turned out that many of the larger stones had a slightly yellow tinge, varying in different specimens from the palest straw to a decided amber colour, and, as this detracted greatly from their value, no little disappointment and loss were sometimes experienced when the gems came to be sold in London and Paris.

One of the first settlements which sprang up on the banks of the Vaal River was a place called Pniel, of which the reader may form some idea from Fig. 332, which is copied from a sketch actually taken from the windows of Jardine’s Hotel. It was then only a little straggling village, chiefly of wooden sheds or corrugated iron erections, with but two or three more substantial structures. The diamonds which were found in this neighbourhood were obtained from gravel which lay on the slopes of the hills rising from the river. The mode of conducting the search for diamonds in these gravels was simple enough. The first operation was the washing of the material, in order to remove sand and dirt, and this process was usually performed at the margin of the river, where the gravel was brought down in carts and deposited in a suitable place, at which a cradle was erected. The cradle was simply a strong wooden framing sustaining sieves of wirework or perforated metal, placed one above the other, those at the top having the largest meshes, so that the lowest would only permit sand or very small pebbles to pass through. The cradle was capable of receiving a rocking movement, and while the gravel was thus sorted, water was freely poured on the uppermost layer, so that the stuff was in a short time thoroughly cleansed and sorted. When this had been accomplished, the gravel was thrown in successive lots on a table, at which the digger sat and rapidly examined it for diamonds by help of a flat piece of wood or iron (see Fig. 328). The larger gems were readily detected, and indeed could be picked out from among the pebbles on the sieve before the stuff was thrown on the sorting-table. Crystals of quartz, which sometimes glisten among the mass, often excited groundless delight in the bosom of the inexperienced worker.

FIG. 332.—_Pniel, from Jardine’s Hotel_ (_c._ 1870).
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On the payment of certain fees, the digger obtained a “claim,”—that is, he acquired the right of working an assigned portion of the soil. But if the claim had been left unworked for a week, it might be, in mining parlance, “jumped”—that is, any person might take possession of it, or jump into it, on procuring a proper licence.

Since the first rush of diamond-seekers to the river-banks, the stones were abundantly found elsewhere, namely, at the “dry diggings,” where the soil, dug out with a pick or shovel, was sifted first through rough sieves, afterwards through sieves having fine wire meshes The sieve, in such cases, was often suspended by thongs of hide between two upright poles, in the manner represented in Fig. 333. The miner was thus enabled to swing the sieve rapidly about, until the sand and dirt were separated, when the remaining gravel was emptied on the sorting-table in the manner before described. As the idea was formerly entertained that diamonds lie only on or near the surface of the soil, the early miners seldom penetrated more than a foot or two beneath the surface. But it was discovered that, so far from it being true that diamonds are present in superficial deposits only, the finest stones are met with at considerable depths to which no defined limit can be assigned; thus in sinking a well large diamonds have been found at 100 ft. below the surface. When these facts became known, many of the abandoned claims were worked over again down to a depth of 30 ft. or 40 ft.

FIG. 333.—_Sifting at the “Dry Diggings”_ (_c._ 1870).
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The rapid rise of localities under such conditions may be illustrated by the case of Du Toit’s Pan, which is the centre of a dry-digging district, and grew in a wonderfully short space of time from nothing to be a town hiving several large hotels, two churches, several public billiard-rooms, a hospital, and a theatre. In 1871 the _claims_ at this place, each 30 ft. square, sold at prices varying from £1 to £50–-the person who worked a claim paying also a small monthly sum for the licence. But those who were lucky enough to have obtained the first possession of the claims at another famous dry-digging locality, named Colesberg Kopje, at the cost of only the licence at 10_s._ per month, must have been still more fortunate, and have realized an enormous percentage on their investments; for, four months afterwards the ruling prices at the last-mentioned place were £2,000 and £4,000 per claim. This great increase in value cannot be wondered at, if the accounts related of the value of the diamonds found here are true. For instance, it is stated that one individual, who just before the great rush had bought a claim for £50, found in it diamonds worth £20,000. Colesberg has become a populous town, with good buildings and regularly laid-out streets, while a great camp of tents and other temporary structures still surround it on all sides.

At all the towns above-mentioned newspapers were published, relating chiefly to matters interesting to the miners—giving, for example, lists of “finds,” with the names of the lucky finders. It is curious that the term “diamondiferous” has, in these localities, come to be used as a general term denoting excellence of any kind. Thus, when it is desired to apply an epithet of superlative praise to a pickaxe or to a piece of furniture, this significant adjective is made use of; and a salesman in the diamond-fields will not hesitate to speak of _diamondiferous_ coats and trousers!

FIG. 334.—_The Vaal River, from Spence Kopje_ (_c._ 1870).
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It will be seen that the early diamond-seekers at the Cape followed very primitive methods, by simply washing in sieves the gravel and sand shovelled out of the river banks; and indeed, it was only when, about 1871, they began to dig deeper that their working seems entitled to be called mining. The “dry-digging” operations began at the since famous Du Toit’s Pan, by the circumstance of a Boer farmer finding to his great surprise diamonds sticking in the walls of his house, which had been built of mud. When the locality of this mud was examined by digging, more diamonds were found; and when the excavation was continued downwards, still more. At this place and at four others, all within a circuit of less than four miles diameter, have been developed the richest diamond _mines_ in the world, throwing into the shade the produce of all the river gravel washings; and what is still more remarkable, showing no signs of exhaustion after nearly thirty years of working, but rather the contrary. The locality soon presented a scene of the most active industry, and it was not long before the town sprang up which has since become celebrated all the world over—Kimberley, the diamond capital. Kimberley is situated at the northern part of the British territory known as Cape Colony, not far within its boundary, and about 14 miles from the Vaal River, in Lat. 28° 43´ S., Long. 24° 46´ E. It lies in a north-easterly direction from Cape Town, at a distance of about 550 miles. When the existence of diamonds at the Cape became known, a great influx of strangers seeking fortune set in to a land that had failed to offer the attractions to colonists that America and Australia did. Before the establishment of the overland route opened a more direct way to India, China, and Australia, Cape Colony owed whatever importance it had to its position as a provisioning and coaling station for ships and steamers. As a British settlement it was little regarded, and its somewhat somnolent condition would have been deepened by the opening of the Suez Canal in 1869, had not the diamond discovery in that very same year brought about a great change. But the early diamond-seekers found their land of promise a wilderness without roads and without habitations, for the development of civilization did not then extend far from the coast. It is true, that here and there, at great distances apart, a few primitive missionary stations might be found, like that of Pniel shown in one of our cuts, which also represent the inhospitable aspect of the country. One cannot but admire the pluck of the adventurers, who, though unversed in their quest, encountered in its prosecution prolonged toils and many hardships. But they were young men, and their perseverance gained its reward. They came from all parts: from Britain, from America, from Australia, from Germany, even from Russia.

The finding at Du Toit’s Pan, and at contiguous places, of diamonds at some depth below the surface of the soil, led to geological examinations of the district, which ultimately resulted in discoveries of the highest interest and importance, as will now be explained, with first a few words about the external features of the country.

A traveller directing his steps northward from the sea-shore at almost any part of the southern coast of Cape Colony will be faced by several successive ranges of mountains, or what will appear to be such, running more or less parallel to the coast, and of no great elevation. When he has reached the summits of these heights he will not find corresponding declivities on the northern side, but nearly level plains, bounded northwards by other similar ranges. Supposing him to set out at a point, say, 150 miles east of Cape Agulhas (the most southern point of Africa), he will, about 50 miles from the shore, have reached the top of the third of the great escarpments which rise up like the stages of a gigantic terrace, and having thus gained the ridge of the Black Mountains, he will see one of these almost level plains stretching before him a breadth of 80 miles, for the most part arid and inhospitable, with a much greater length east and west, and bounded on the north by a portion of the range of elevations that in an almost unbroken line runs through Cape Colony to Delagoa Bay nearly parallel with the coast, at a distance from it between 100 and 150 miles. This extensive plain is known as the _Groot Karoo_ (Great Karoo),—_karoo_ being the generic name for such plains in South Africa. After crossing the Great Karoo, our traveller, on mounting the last far-reaching step of the Brobdignagian staircase, may find himself on the summit of the Nieuveldt Mountains, at an altitude of nearly 10,000 feet above the sea-level, attained in several widely separated stages within a distance of 140 miles. From the summit of these elevations there is no descent by terraces northwards, but the high tableland or plateau stretches away for hundreds of miles, descending by only a gentle slope towards the Orange River, but maintaining an average altitude of nearly 6,000 feet, and extending far beyond the Orange River towards the Equator. Kimberley is situated about 50 miles north of the Orange River, and 4,042 feet above the sea-level.

It was soon observed that the Karoos had common geological characters, consisting in a certain series of shales, coal, limestones, etc., and this series naturally came to be called the “Karoo formation,” just as we in England speak of the Wealden formation, etc.; and it was found that it extended over a greater part of Central South Africa, covering an area of at least 200,000 square miles, with an estimated thickness of 5,000 feet. The reader need not imagine that a boring nearly a mile in depth had to be made for the ascertainment of this last dimension, if he will remember what has been said in the last paragraph about escarpments of the rocks looking everywhere towards the coast. There is reason to believe that these beds were originally the sedimentary deposits of a vast fresh-water lake, or inland sea, far back in geological times. But here we need only concern ourselves with the development of the Karoo beds about Kimberley. There the ground is covered by a sandy soil of a red colour, for it contains much iron. Below this there is a layer of decomposed basalt, also containing much iron, its thickness varying from 20 to 90 feet. This lies upon a bed of very combustible shale, with carbon and iron pyrites, 250 feet thick, which from its great development here is known as Kimberley shale; then, after a conglomerate stratum 10 feet thick, is found a very hard compact rock, resembling hornblende, extending 400 feet downwards, and resting on another hard rock of quartz, also 400 feet in depth. These beds are _nearly_ horizontal, but dipping a little towards the north. In speaking of them collectively we may use the local term of the miners and call them “the reef.”

Now, there are a few certain spots near Kimberley, and two or three elsewhere, in which the strata forming “the reef” are not found, but something quite different. These may be compared to large dry wells, extending vertically downwards to unknown depths, which have been filled up with matters from below. They are called _pipes_, but they are uncommonly large ones; for though of a somewhat irregular circular or oval shape, their diameters range from 200 to 500 feet. Nor must it be supposed that the enclosing reef presents itself as a smooth wall, as the name “pipe” might suggest. These _pipes_ are true diamond mines. They are believed to have been formed by an eruptive action originating from below at a great depth, and this was not by the escape of red-hot lava or other molten rocks, but by that of steam or other gases. It is known that the eruptive forces acted from below, for the edges of some of the strata are seen in places in the walls of the reef that surround the pipes to be turned a little _upwards_. It is known that the erupted matter was not molten lava or rock, for the shale and other strata show none of those changes of character near the pipes which would have resulted from igneous action, and for the same reason the gas or steam that escaped by these pipes could not have been highly heated. It must therefore have forced its way through the strata by enormous tension or pressure, and this either at one terrific outburst or possibly by the gradual enlargement of smaller volcanic chimneys. These blow-holes are filled with a mixture of subterranean débris, as if mud had been forced up from below, carrying with it an extraordinary variety of rock fragments and crystallized minerals. These are embedded in a mass of a bluish-green colour much resembling indurated clay (but nearly as hard as ordinary sandstone), and this on long exposure to the weather crumbles down to a yellow friable substance. More than eighty different kinds of minerals of the volcanic class have been found in this _breccia_, as it is termed by geologists, and it is remarked that these fragments could not have been exposed to any great heat, for their edges show no signs of fusion. There are also embedded in the agglutinating substance large masses of the surrounding strata, sometimes having an area of several thousand square feet, and these are called in miners’ parlance “floating reef.” The cementing material is named “blue ground,” and the same when crumbled down by exposure is known as “yellow ground.” These colours are due to oxides of iron, which in the unaltered ground give the blue-green tint, being lower oxides; but are converted by absorption of oxygen into yellow and higher oxides. The upper part of the pipes is filled to a depth of about 70 feet with “yellow ground,” produced by the penetration of atmospheric influences. Blue ground and yellow ground alike contain diamonds, and the yield of these is pretty regular at all depths in the same mine (some have been explored down to nearly 2,000 feet), although it varies considerably from one mine to another, and in some the east side is often richer than the west. Thus in one load (1,600 lbs.) of _ground_ from Du Toit’s Pan, in 1890, the quantity of diamonds found averaged less than 2 grains (0·5 carat), while Kimberley yielded 1·25 to 1·5 carats (5 to 6 grains). It is singular that the stones from mines quite close together are so distinctly different in character, that the Kimberley merchants can tell at once the source of any particular parcel. This would indicate that the blue mud was not forced up the several pipes at one and the same time, carrying with it diamonds from one birthplace.

The existence of the diamondiferous pipes is pointed out by no indication on the surface, which is covered nearly uniformly with the red sandy soil already spoken of; although indeed the site of the Kimberley mine was marked by a slight elevation, and that of Du Toit’s Pan by one of the depressions there called _pans_, which, at least in the wet season, are receptacles for surface water. The Wesselton mine, which was found only in the last decade of the century, about a mile from Du Toit’s Pan, also showed a surface depression, and that had been utilised as a depositing place for dry rubbish. At a later period the “Leicester mine” was accidentally discovered 40 miles away. At Jagersfontein, in the Orange River Free State, 60 miles from the Kimberley mines, is another pipe which yields the finest diamonds of any, commanding prices nearly the double of those paid for the De Beers and Kimberley gems, being in fact their nearest commercial rival. The proprietorship of the Kimberley group having in 1889 become united in the hands of one company, known as the “De Beers Consolidated Mines,” this company is able practically to control the diamond market, as it has sometimes turned out in a year as much as 3 million carats of diamonds, which sell for about £3,500,000. Up to the end of 1892, 10 tons of diamonds had been derived from these mines, representing a value of £60,000,000 sterling. In 1895, the De Beers Company sold diamonds to the amount of £3,105,958, the total expense of working for that year being £1,704,813,—the net profit was £1,401,145. The effect of consolidating all the Kimberley diamond interest into the De Beers Company has been to give an almost complete monopoly to this last, which has however found it advantageous to restrict its production to an annual output of about £3,000,000 in value, as the putting of a larger quantity of diamonds on the market would cause lowering of their price, and a diminution of the profits all round. The reason is, that though the world at large annually spends between 4 and 4½ million pounds sterling in the purchase of diamonds, yet it would not by a reduction in their price be induced to spend proportionately more. The company are sufficiently supplied by only two of their mines, the Kimberley and the De Beers, the expenses of working these being also relatively smaller than is the case with the others. It may be of interest to compare the quantities of diamonds that have so far been produced from the world’s greatest fields, leaving out Borneo, the Ural Mountains, Australia, etc., as comparatively insignificant. Estimated produce of India, from the remotest period, 10 million carats; of Brazil (since 1728), 12 million carats; of South Africa, in only 19 years, 57 million carats.

At the time of the discovery of the Kimberley mine (July 1871) it was divided into about 500 claims, each 31 feet square, and between these were roadways across; but when the claims were excavated to a depth of 100 feet or more the roadways became unsafe, and, the “blue ground” underneath them being too tempting always to be left for their support, they began to fall in, and the mine was often threatened with ruin from this cause. The state of things became still worse when the unsupported walls of the “pipe” itself began to collapse, so that by 1878 a quarter of the claims were buried in the ruins of the reef. These falls continued, and although very large sums were year after year expended in removing the fallen reef, the cost amounting in 1882 to 2 million pounds sterling, it was found at last that very few of the claims could be regularly worked, and when in 1883 a tremendous fall of 250,000 cubic yards of reef took place, covering half the area of the mine, it became necessary to adopt another mode of working, namely, a regular system of underground mining. Vertical shafts were sunk at a considerable distance from the pipe itself, and tunnels from these carried through at different levels, with a system of galleries so arranged that all the “blue ground” is removable without danger to the miners. The whole mine is illuminated by electric lights, and the different kinds of labour are carried on by distinct sets of workmen, some of whom drill holes for the reception of dynamite cartridges, others shovel the material into trucks, others again wheel the trucks along tram lines, which converge to a space where their contents are discharged into skips holding four truck loads, in which they are hoisted to the surface at about the rate of 400 loads per hour. This goes on day and night, the miners working in three shifts of eight hours each. About 8,000 persons are employed, 6,500 of whom are blacks.

Fig. 334_a_ is a sketch section of the Kimberley diamond mine, approximately to scale, and a glance at this will elucidate the foregoing description. The thick vertical and horizontal lines show the positions of the shafts and galleries that have at various times been excavated, the lowest gallery being connected with a shaft a considerable distance from the pipe, towards the right, but out of the range of the sketch. The fringed lines at the top, with dates, give some idea of the forms of the excavations until the final fall of reef that determined the resort to subterranean working.

FIG. 334_a_.—_Sketch Section of the Kimberley Diamond Mine._
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When the “blue ground” has come to the surface, how are the diamonds to be extracted from the hard mass? how can a stone of a few grains weight be found amongst 1,600 lbs. of miscellaneous matter—a thing perhaps not larger than a peppercorn in four cubic feet of compact material? The “blue ground” is spread out on levelled and carefully prepared areas called “depositing floors,” and there, after a few months’ exposure, all but the very hardest pieces crumble down, the atmospheric action being accelerated by turning the material over with harrows, and by occasional waterings. The “blue ground” from the De Beers mine requires at least six months of this treatment, and it contains a certain proportion of refractory lumps that would not disintegrate in perhaps less than two years. These lumps are coarsely crushed between rollers, and the fragments are spread over slowly moving tables, from which any larger diamonds are picked off; the fragments left go through smaller crushers, and are subjected to still greater concentration. The depositing floors of the De Beers mine are laid out as rectangles, 600 yards long by 200 yards wide, each holding about 50,000 loads. They occupy several square miles, and as the “blue ground” spread upon them is always one of the most valuable assets of the company, the quantity of it forms an important item in the balance-sheets, and the amount that can be realized from it can be estimated with sufficient closeness, on account of the nearly uniform distribution of the diamonds. Thus in June 1895, the 3,360,256 loads then on the floors were put down as equivalent to nearly 1 million pounds sterling. When the “ground,” thoroughly weathered, has become yellow and friable, it is transferred to the washing machinery, by which about 99 per cent, of the original non-diamondiferous material is removed, and, thus concentrated, the gravel is together with the mechanically crushed material submitted to the action of a machine called the _pulsator_, where the gravel is first assorted into sizes by being turned about within an inclined iron cylinder perforated with several stages of round holes of diameters successively of 2, 3, 4 and 6 sixteenths of an inch. The pieces that are too coarse to pass through the largest holes are taken to the _sorting house_ direct; but the stones that have passed through the cylinder drop according to their sizes into four separate sieves called at Kimberley _jigs_, from the well-known mining term _jigger_, applied to a man who washes ores in a sieve. The several jigs into which passes the now assorted gravel have screens with meshes corresponding to the holes in the cylinder; and by a very ingenious arrangement the concentration is carried to the point at which the diamonds can be individually picked out. The “jigs” themselves do not move, but all over the meshes of the screen is spread a layer of leaden bullets, which prevent a too rapid passage through the screens, while the material is kept moving in water, by that liquid _pulsating_ or emerging in quickly succeeding gushes from below the meshes, and thus carrying off the lighter matters, while those of greater specific gravity, including the diamonds, work their way downwards between the bullets and through the meshes, and are received in boxes which are periodically carried to the sorting house.

When the now much concentrated diamondiferous gravel reaches the sorting house, the remaining operation consists merely in picking the diamonds out. But simple as this operation is, it has to be conducted systematically. In the sorting house are long tables covered with plates of iron, and placed in a good light. Upon these is thrown the wet gravel, but not promiscuously; the different sizes being set apart, the sorter spreads out the heap before him with a flat piece of zinc, picks out the diamonds and drops them into a small box. Only white men in whom confidence can be placed are allowed to deal with largest sized material, for this offers the strongest temptation to purloiners, as in this of course the most valuable stones are met with. This material, after the first search, is submitted to the scrutiny of another person, to see that no diamond has been overlooked; but the smaller assortments are examined by blacks, who are closely supervised by white men. The value of the diamonds occasionally sorted out in a single day may reach £10,000.

At the diamond mines little trust is reposed in the honesty of the blacks. Below ground and above ground they work under the constant surveillance of white men, and they live in “compounds” which are spacious areas—perhaps of 20 acres in extent—enclosed by lofty iron fences, and containing long rows of corrugated iron erections divided into rooms, each appropriated to a score of natives. Food, etc., is supplied from a store at less than ordinary prices, and the company find fuel and water gratis, and provide a well equipped hospital and medical attendance. There are swimming baths, and ample recreation grounds for dancing, etc. The natives of each of the many tribes keep by themselves apart, and follow their own fancies. They receive good wages, and some of them save money. They are not allowed out of the “compound” or the mine, except to work on the depositing floor, which they do under guard. They accept their restrictions voluntarily, making agreements for a certain term, three months being the least. Those who leave, as many do to spend their earnings, often “not wisely but too well,” usually return. The depositing floors are surrounded by fences 7 feet high, unscalably and impenetrably armed with barbed wire; and as here robbery would have the readiest chance, where the largest stones might be met with, extraordinary precautions are taken, watch and ward being maintained by day and by night. Not more vigilantly did Cerberus keep the entrance of Pluto’s domain, nor the wakeful dragon guard the golden apples of the Hesperides, than the patrols observe the depositing floors. At night powerful electric searchlights are made to play across the enclosures, so that unauthorized movements can scarcely escape detection. Besides these provisions against theft, the laws of the Colony prohibit any attempt at illicit dealing in diamonds, under a penalty of two years’ penal servitude.

The maximum penalties for contravention of the Diamond Laws are, however, much more severe, and that to an extraordinary degree. Thus any unlicensed dealer is liable to a fine of £1,000, or fifteen years’ imprisonment, or both. And the authorized dealers are required to keep a most minute record of all their transactions, to send a copy of it every month to the head of the police, and to produce it when required. It is needless to say that extraordinary precautions are taken to prevent the native workmen from secreting diamonds. And any person even finding a diamond, and neglecting to report the circumstance to the proper quarter at once, is liable to the pains and penalties above mentioned.

The “blue ground” was at first supposed to be the original home of the diamond, within which it had somehow taken its shape. But no satisfactory explanation was forthcoming as to the state of the carbon before its solidification into the crystalline form. The more general opinion has been in favour of a volcanic origin due to very high temperature; and although the “blue ground” itself is clearly not the ordinary erupted matter of volcanoes due to igneous fusion, the geology points to the district having been the scene of very active and extensive volcanic energies at more than one remote period, for the bed of the Karoo inland sea has been several times covered by level sheets of molten matter extruded somewhere from below; but not through the “pipes,” which were blown out ages afterwards. The strata of basalt and of hornblendic mineral, which extend horizontally over great areas in the Karoo formation, are of igneous origin, as are also some nearly vertical dykes of trap rock, about 7 feet wide, that are found traversing the “blue ground” in certain directions. These intrusive dykes are of course more recent than the formation of the blue ground, and that is itself later than the production of the pipes. The fact of many fragments of crystals being found in the “blue ground” does not comport with the theory that supposes it to be the matrix; and besides this, many of the diamonds show scratches, and as these are producible only by other diamonds, it would appear that they must all have travelled in company, some part of their journey at least.

Carbon in any form is quite infusible at the highest temperature we have hitherto been able to produce, although an incipient softening under the influence of the electric arc has been suspected. Professor Dewar, an English chemist, basing his data on analogies with other substances, and on purely theoretical grounds, has calculated that the melting temperature of carbon is near 3,600° C. (6,512° F.), and that it cannot remain in a liquid state at a temperature exceeding 5,527° C., when its vapour would have a tension equivalent to a pressure of 15 tons on the square inch. So far as these deductions are correct, both the melting point of carbon and the boiling point of its liquid must lie within the range of temperature expressed by 3,600° C. and 5,527° C. The most intense heat we can produce is that developed in the electric arc discharge, and an eminent French chemist and metallurgist, M. Moissan, by employing special arrangements and very powerful currents, has thus been able to obtain in his “electric furnace” a temperature estimated at 3,500° C., which nearly approaches the lower of the above-mentioned limits, and he has thereby produced many new and unexpected chemical combinations of refractory elements. Among the most striking of his results is the formation artificially of real crystalline diamonds. He found that carbon is freely dissolved by several of the metals in fusion at the temperature of the electric furnace. When the carbon separated from the metals, as they cooled and became solid, it was always in the condition of graphite. The carbons of the electric poles were readily attacked by molten iron, and it was from the solution of carbon in iron that Moissan prepared his diamonds. The fact of carbon thus combining with iron was of course no discovery, as the reader already knows; and the resulting combination was found, on allowing the metal to cool, to be simply cast iron, the greater part of the carbon separating out in the graphitic form. But M. Moissan, having studied the conditions of the Kimberley mines, and recognizing the probability of the diamonds having taken their origin at very great depths, where the pressure due to the weight of superincumbent strata would be immense, was struck with the idea of _pressure_ being in some way a factor in their formation; and it occurred to him that the carbon might separate from its liquid condition in the iron in the crystalline, and not in the graphitic form, if the solidification could be effected under great pressure. The apparently insurmountable difficulty of applying an enormous pressure to a small quantity of molten iron (half a pound) yielded to the experimenter’s ingenuity. He took advantage of the circumstance that cast iron at the moment of solidification expands, a property upon which depends its use for many purposes. If then the fused mass were suddenly cooled on the outside, we should have a shell of solid iron enclosing a nucleus of still fluid metal, which, on cooling in its turn, would tend to expand, and by so doing would exert a great pressure within the shell by which it was confined. At first Moissan plunged his glowing crucible into cold water, but a method of more rapidly cooling it was to immerse it in melted lead. It seems a strange proceeding to cool the crucible by surrounding it with hot metal, yet the _difference_ of the temperatures was sufficient to produce the desired effect, the cooling contact of water not really operating on the intensely heated body, which becomes separated from the liquid by a coating of _steam_. When the mass of iron was dissolved off, diamonds of all kinds were found in the residue, and, though extremely small, some crystals were perfect in shape and colour; every variety that occurred in the mines being found reproduced in tiny size. There was also some graphite in the residue. Many more crystals of “pure water” were obtained by the lead-cooling than by the water-cooling, as the former process gave some flawless cubes and octahedra. The largest of the set was only 1/50 inch across, and although of perfect form when first extracted, within the course of three months it had spontaneously split up into fragments.

There was evidently no danger of M. Moissan’s manufacture of diamonds from coke causing consternation at Kimberley; though it would not be without interest to speculate upon the consequences had the French _savant_ achieved the greater triumph of turning out carbon crystals in every respect equal to the productions of nature’s own laboratories. What a drop there would have been in the shares of the De Beers Mines Consolidated! What heaviness of heart would have fallen upon those great ladies who exult in the exclusive possession of priceless tiaras and precious necklaces flashing with the resplendent gems! From a scientific point of view, M. Moissan’s fabrication of even those minute crystals, which so soon spontaneously crumbled into fragments, is a distinct and valuable success; for, notwithstanding their diminutive size and instability, they show us that art has so far succeeded in imitating the processes of nature, that some of her secrets have been revealed. Though we know the exact chemical composition of all kinds of crystallized minerals, very very few of these have we been able to imitate artificially. Nor is this to be wondered at; for nature’s resources are immense compared with ours: she can command temperatures unlimited by which to form her solutions or liquefactions; prodigious pressures to keep them close; and time immeasurable—geological time—in which to let them cool, and their particles freely coalesce into geometric forms. Human agency, being obviously unable to reproduce, even on the smallest scale, such conditions as attended the deposition and slow cooling of the earth’s crust, may not hope to rival the products of the planet’s prime. So the fair owners of the earth-born gems may possess their souls in peace, free from any fear of the chemists’ crucibles; and the Kimberley Diamond Companies are not likely to suffer panics from the results of scientific researches, and probably will continue to pay their handsome dividends for time indefinite.

But curiously enough, a discovery of the latest years of our century has revealed the existence of diamonds in a region not mapped by the most advanced of geographers—a region which indeed cannot be defined by degrees of latitude and longitude. In the recesses of an unquestionable meteorite—one of those celestial lumps of iron of which mention has been made in the earlier pages of this volume—real diamonds have been found. These quite resembled the products of M. Moissan’s experiments, being extremely small, but including clear and perfectly shaped crystals, associated with black ones, and also with much graphite in more or less definite forms. So very limited, however, could be the quantity of diamonds obtainable from this hitherto unsuspected source, that even if they rivalled in quality the finest stones from the South African mines, it might be difficult to form a “Company” for their _exploitation_. Still, there is the possibility of some one falling in with a little meteorite containing some mature full-sized carbon crystals, and such a one might be considered equally fortunate with the finder of the famous Australian nugget “Welcome” (£25,000). The association of diamonds with the ferruginous matter of the “blue ground” in the Kimberley pipes, their crystallization out of iron in M. Moissan’s experiments, and their presence in iron meteorites, would seem to point to special relations between the two elements, iron and carbon. Some of these relations are exemplified in another way by the profound modification effected in the physical properties of iron, by its combination with a very small quantity of carbon, as in some kinds of steel; or again, by the differences between white cast iron and grey cast iron, as determined by the condition of the carbon in each.

FIG. 335.—_Portrait of Sir Humphrey Davy._
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NEW METALS.

The chemistry of the nineteenth century can boast of a series of discoveries more brilliant and more numerous than ever belonged to any other science within a like period. And the advantage to the world must have been great, for chemistry more directly than any other branch of knowledge ministers to the useful arts and promotes the comfort and well-being of society. The science itself, as it now exists, is almost the creation of the present age. But its recent developments cannot be here discussed; nor, of the immense number of new products with which it has enriched the world, can more than a very few be brought under the reader’s notice in the remaining pages of the present work. Among the most striking of the remarkable series of discoveries by which Sir Humphrey Davy penetrated the mysteries of matter was the isolation of the alkali metals—a circumstance which marks an important era in the history of chemistry. That the alkalies were oxides of unknown metals had indeed been previously surmised by chemists, from the fact of their behaving like metallic oxides in neutralizing and combining with acids to form the class of compounds called _salts_. All attempts to decompose these alkalies had proved fruitless until Davy separated the metal _potassium_ from potash, in 1807. When, however, this alkali had once been proved a compound, more correct ideas were introduced into chemical science; the nature of other alkalies and earths was explained in like manner, and new and powerful re-agents were placed in the hands of the chemist.

Davy first obtained potassium by exposing to the action of the voltaic current a fragment of potash which had become moist on the surface by exposure to the air. The battery was formed of the then unprecedented combination of two hundred pairs of 6–inch plates on Wollaston’s plan, which was constructed for the Royal Institution of London. The heat produced by the passage of the current fused the potash, and globules of metallic potassium were separated at the negative wire. This method yielded the metal in very small quantities only, and at a great cost. Gay Lussac and Thenard soon afterwards found that potassium could be obtained more cheaply and in greater abundance when fused potash was made to flow over iron-turnings heated to whiteness in a gun-barrel, and the hydrogen and potassium vapour were passed into a cooled receiver, in which the latter body was condensed. The metal is now obtained by heating potassium carbonate with charcoal. For this purpose it suffices to heat crude tartar in a covered vessel from which air is excluded. The tartar is first calcined in a crucible until all combustible vapour has been driven off. The charred mass, which now consists of potassium carbonate mixed with finely-divided carbon, is then broken into lumps and quickly introduced into a wrought-iron retort, which is heated in a furnace to nearly a white heat. A receiver in the form of a flat iron box, 12 in. long, 5 in. wide, and ¼ in. deep, is adapted to the neck of the retort, and is kept cooled by the application of a wet cloth on the outside. The potassium thus obtained is not pure, and it must be distilled in an iron retort, as otherwise a powerfully detonating compound is apt to be formed by a portion of the metal combining with carbonic oxide.