Page:Popular Science Monthly Volume 56.djvu/81

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73
EMIGRANT DIAMONDS IN AMERICA.

not direct, so to speak, our trumpet to the earth, instead of letting its utterances skim over the horizon? In regard to this suggestion, we know certainly one fact from our laboratory experiences: that these magnetic waves, meeting layers of electrically conducting matter, like layers of iron ore, would be reflected back, and would not penetrate. Thus a means may be discovered through the instrumentality of such waves of exploring the mysteries of the earth before success is attained in completely penetrating its mass.

 
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EMIGRANT DIAMONDS IN AMERICA.
By Prof. WILLIAM HERBERT HOBBS.

TO discover the origin of the diamond in Nature we must seek it in its ancestral home, where the rocky matrix gave it birth in the form characteristic of its species. In prosecuting our search we should very soon discover that, in common with other gem minerals, the diamond has been a great wanderer, for it is usually found far from its original home. The disintegrating forces of the atmosphere, by acting upon the rocky material in which the stones were imbedded, have loosed them from their natural setting, to be caught up by the streams, sorted from their disintegrated matrix, and transported far from the parent rock, to be at last set down upon some gravelly bed over which the force of the current is weakened. The mines of Brazil and the Urals, of India, Borneo, and the "river diggings" of South Africa either have been or are now in deposits of this character.

The "dry diggings" of the Kimberley district, in South Africa, afford the unique locality in which the diamond has thus far been found in its original home, and all our knowledge of the genesis of the mineral has been derived from study of this locality. The mines are located in "pans," in which is found the "blue ground" now recognized as the disintegrated matrix of the diamond. These "pans" are known to be the "pipes," or "necks," of former volcanoes, now deeply dissected by the forces of the atmosphere—in fact, worn down if not to their roots, at least to their stumps. These remnants of the "pipes," through which the lava reached the surface, are surrounded in part by a black shale containing a large percentage of carbon, and this is believed to be the material out of which the diamonds have been formed. What appear to be modified fragments of the black shale inclosed within the "pipes" afford evidence that portions of the shale have been broken from the parent beds by the force of the ascending current of lava—a