Зображення сторінки

atoms are set vibrating by the impulse communicated to them from the blue rays of the spectrum (those principally active in producing the phenomenon), is not an explanation, but another mode of stating the fact. The same effect can be produced by the application of mild heat or slight friction, and some specimens emit light when excited by electricity. The electrical susceptibility of this stone was known to the ancients, although they were probably not aware that mere change of temperature sufficed to call it into operation.

But the quality which most markedly distinguishes the diamond from all other gems, is its combustibility. This peculiarity is of comparatively recent discovery. A conjecture of Boetius de Boot,' and an inconclusive attempt on the part of Robert Boyle, led the way to the celebrated experiment of the Florentine Academy in 1694, when a diamond, placed at the focus of a large concave mirror exposed to the rays of the sun, was ignited and consumed before the eyes of Cosmo III. and his court. The question as to the chemical composition of the gem was thereby rendered of comparatively easy solution. Lavoisier, in 1775, showed that the product of combustion was carbonic acid gas. Sir Humphry Davy proved this substance to be the sole product. Mr. Smithson Tennant demonstrated that equal weights of diamond and charcoal yielded, in combination with oxygen, precisely equal quantities of carbonic acid. The proof was thus complete that diamond is nothing but crystallised carbon; a fact not the less surprising that it has become familiar.

This extreme simplicity of constitution seemed irresistibly to invite, and long successfully baffled the artificial production of the gem. Carbon is one of the most intractable bodies in nature. Its singular flexibility in some directions is compensated by an equally singular rigidity in others. At no attainable temperature can it be either liquefied or vaporised. No acid attacks it. It is wholly insoluble in water, and, under ordinary conditions, in every other known substance. The problem then how to obtain crystals of an element which can neither be melted, volatilised, nor dissolved, was evidently one of exceptional difficulty. An obvious preliminary inquiry was as to the method pursued by nature for the attainment of this end. By what process were diamonds formed in the vast primeval laboratory? On this point the widest possible divergences of opinion have existed, and still exist. Some ascribe to them a vegetable, some an animal, some a mineral origin. On one side it is maintained that a high degree of heat was necessary for their formation. On the other, it is asserted that nothing regarding their origin is certain except that they were produced at a comparatively low temperature. One writer invokes the vague, but potent agency of electricity. Another points to the antique association of these problematical crystals with “thunderbolts. A third brings to bear

" Emil Kluge, Handbuch der Edelsteinkunde.

the unimaginable pressure of miles of superincumbent strata. the frequency of their occurrence in company with gold, the ancients concluded diamonds to be the “flower,' or sublimation of the finest particles of that precious metal. By a somewhat closer process of reasoning, founded on his observation of the high refractive power of this gem, as compared with its specific gravity, Newton was led to the inference that it was an “unctuous substance coagulated.' And his authority largely contributed to establish and maintain the doctrine of its organic origin. We believe, however, that a close consideration of the circumstances under which it is actually found in nature, leads to a directly opposite conclusion.

The first fact to be noted regarding the native haunts of the diamond is that it occurs almost exclusively in alluvial deposits. Indeed, the early Brazilian explorers sought for it only in river-beds, turning the stream, and digging through the superficial clay to the quartz gravel or cascalho beneath, where the gem was usually discovered in company with gold dust, garnets, spinel, emery, diaspore, and other rare minerals. From this connection came the use of the phrases pure water,' 'finest water,' &c., to denote the quality of the stones. Subsequently, the workings were carried on with equal success in dry deposits, which were, however, everywhere of the same general character. Similar conditions prevail in India, Australia, at the Cape, and in the Ural mountains. It is evident that the


is here met with, not in the character of a denizen, but of a pilgrim. The home where it was born and bred must be sought elsewhere. On further inquiry, it appears that the water-borne fragments with which it is associated are the débris of an ancient quartz rock, called itacolumite. Wherever this particular formation occurs, the diamond has hitherto been found invariably to accompany it, and in one part of Brazil it has even been discovered embedded in the mountain itself. It is not, then, going too far to assume.(although even this has been doubted), that we have here the original matrix of this precious substance. Now the itacolumite belongs to the class of rocks known as “metamorphic.' That is to say, it was originally deposited in water, but was subsequently so altered by heat as to lose all trace of stratification. The particles of which it is composed were derived from the primitive granite or gneiss, and are almost

It is needless to observe that it exhibits no trace of organic remains.

The diamond-beds of South Africa were deposited in the basin of a vast inland lake. The so-called Karoo-formation to which they belong, occupies 200,000 square miles, and possesses an average thickness of 5,000 feet.13 The stones are at present discovered in two classes of position—in “river diggings, and in dry diggings.' The river diggings exbibit the ordinary characteristics of alluvial washings, but the dry diggings are remarkable as being apparently

pure silica.

the result of volcanic action. They consist in circular depressions, or • pans, filled with a species of detritus, evidently (as shown by the upward displacement of the horizontal shales at the edges) intruded from below. Beneath some superficial layers of sandy soil and calcareous tufa, diamonds are found in a breccia of shale and sandstone, together with garnets and nodules of iron pyrites. The miners assert that the stones extracted from each separate pipe' have a character of their own, and—like salmon from affluents to the same estuary-can be distinguished by the practised eye. This, however, we may safely set down as a digger's legend; for it can scarcely be supposed that the volcanic activity displayed in the production of these pans' has had any other effect than that of bringing to light the hidden treasures of deep-lying strata, and thus, by different means, attaining the same result accomplished elsewhere by the wearing of river-beds.

The circumstances under which diamonds occur are thus seen not to be materially different in South Africa from what they are in other parts of the globe. Everywhere they are found in alluvial deposits, formed by the disintegration of itacolumite, or some similar sandstone rock, and everywhere their presence is associated with that of gold, platinum, and palladium, of rare minerals and precious gems. A connection that is persistent cannot be fortuitous; and it is reasonable to presume an analogous origin where we find a coincident history. Thus the hypothesis according to which diamonds are separated from all otber precious stones, and assigned a place amongst fossil resins, has a well-grounded presumption against it. The constitution of the rock in which these crystals have been discovered, renders it practically certain that they were formed at a very high temperature; and we may add, with extreme probability, the condition of great and continued pressure. Of the many theories as to their genesis propounded of late years, that which regards them as produced by the sublimation from the internal parts of the earth of carbon, either pure, or combined with some other substance (chlorine, for example), offends least against the ordinary laws of probability. On the other hand, some countenance is lent to the view that they originated in the liquefaction, at great depths, of carbonic acid gas, by the singular fact that some of these gems are found to be explosive in their nature. Quite recently a rose diamond was inspected by the Academy of Sciences at Philadelphia, which had exploded with some violence when incautiously exposed to sunshine on the sleeve of its elegant owner. An appreciable proportion of those extracted from some of the Cape diggings split or crack from the action of internal forces soon after their emergence to the light; 14 and, more than two centuries ago, Tavernier relates that a mine near Raolconda was closed by order of Shah Jehan because the stones discovered there flew to pieces at the first touch of the wheel. It seems, then, unquestionable, whatever view of their origin we may prefer, that certain of these crystals contrived, while still in process of formation, to entangle in their substance some portion of a highly volatile fluid (presumed to be carbonic acid), which, after the lapse of thousands, or it may be millions, of years, exerts unwelcome energy in the disruption of its costly prison-house.

Enough has been said to show that the process by which diamonds came into being in the hidden places of the earth cannot readily be ascertained, even if it could easily be imitated. But, in truth, the puny forces at the chemist's command are wholly incommensurable with the vast powers exerted in the universal manufactory; and—what tells still more heavily against him—the time during which those forces act disappears utterly in comparison with the long ages of the world's slow becoming. The infinite leisure of nature contrasts strangely with the counted moments of a busy human life. The would-be gem-maker is then thrown back upon his own resources, and experiment, not inquiry, is plainly the road for him to follow. If the goal is to be reached, it must be by striking out a short way, not by following in the devious track of natural operationis.

So long ago as 1853, M. Despretz attempted to form diamonds by the prolonged action of electricity on carbon in a vessel exhausted of its air. At the end of some months, during which a strong current was kept continually passing, the platinum wires constituting the negative pole were perceived to be covered with fine black dust from the carbon cylinder at the positive pole. This dust, when examined with a microscope, was found to contain octahedral crystals, black and opaline white, which burned without residue, and acted in every respect like diamond powder. This experiment was evidently of scientific, not of commercial interest. Crystals so minute as to escape detection by the naked eye could show no reason for their continued production; and, accordingly, this and similar attempts, equally ingenious, but even less successful, were gradually relinquished and forgotten. Of late, however, semi-extinct hopes have been revived, and flagging interest has been stimulated by an important advance in another department of what has been called “synthetic mineralogy.' MM. Fremy and Feil, of Paris, by a process, the details of which need not here be dwelt upon, have succeeded, it is said, in producing in considerable quantity the substance known to mineralogists by the generic term of corundum,' and to jewellers, according to the different colouring matters mixed with it, by the specific designations of ruby,' emerald,' and . sapphire.' This substance is, in fact, pure alumina, which had hitherto been crystallised artificially only with the utmost difficulty, and on a very small scale. The announcement of this result could hardly fail to excite chemists to a still higher ambition, and accordingly, a severe competition in diamond manufacture has engaged, and still occupies, many of the laboratories of Great Britain.

well knew by this time, though seldom foreclosed by it now, as he ha been, before he became a Danish citizen. He was sure that she has some good reason for her silence; and the next day he found that the girl who had left her home, through Cadman's villany, was akin, bu her mother's side, to Mistress Precious. But he had another matie to discuss with her now, which caused him some misgivings, yet had better be faced manfully. In the safe philosophical distance of Port from this strong landlady, he had (for good reasons of his own) pointed the place of meeting with Sir Duncan Yordas at the riz hostelry, the Inn of Thornwick. Widow Precious had a mind of uncommonly large type, so lofty and pure of all petty emotions, that if anyone spoke of the Thornwick Inn, even upon her back premis her dignity stepped in and said — I can't abide the stinkin' naam o'un.'

Of this persistently noble regard of a lower institution Mr. Mordacks was well aware; and it gave him pause, in his deep anxiety to spare a tender heart, and maintain the high standard of his breakfas kidneys. “Madam,' he began; and then he rubbed his mouth with the cross-cut out of the jack-towel by the sink, newly set on table. to satisfy him for a dinner-napkin. Madam, will you listen, while I make an explanation ?'

The landlady looked at him, with dark suspicions gathering.
Joost spakoot,' she said, "whativer's woorkin' i' thah mahnd.

*I am bound to meet a gentleman near Flamborough to-morror. Mr. Mordacks continued, with the effrontery of guilt ; "who wil come from the sea. And, as it would not suit him to walk far inland, he has arranged for the interview at a poor little place, called the Thorny Wick, or the Stubby Wick, or something of that sort. I thought it was due to you, madam, to explain the reason of my entering, even for a moment--'

Ah dawn't care. Sitha—they mah fettle thee there, if thon's fondhead enew.'

Without another word she left the room, clattering her beary shoes at the door ; and Mordacks foresaw a sad encounter on the morrow, without a good breakfast to “fettle’him for it. It was not in his nature to dread anything much, and he could not see where be had been at all to blame; but rather would he have taken ten per cent. off his old contract, than meet Sir Duncan Yordas, with the news he had to tell him.

One cause of the righteous indignation, felt by the good mother Tapsy, was her knowledge that nobody could land just now, in any cove under the Thornwick Hotel. With the turbulent snow-wind bringing in the sea, as now it had been doing for several days,

he fishermen's cobles could not take the beach, much less any stranger craft. Mr. Mordacks was sharp; but an inland factor is apt to overlook such little facts marine.

Upon the following day he stood in the best room of the Thorn


« НазадПродовжити »