Discoveries and Inventions of the Nineteenth Century

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 700care 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 701out: 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, 702in 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). 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 703been 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). 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