EMIGRANT DIAMONDS IN AMERICA. 73 



not direct, so to speak, our trumpet to tlie 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 in- 

 strumentality of such waves of exploring the mysteries of the earth 

 before success is attained in completely penetrating its mass. 



EMIGEANT DIAMONDS IN AMEEICA. 



Bt Prof. WILLIAM HERBERT IIOBBS. 



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 min- 

 erals, the diamond has been a great w^anderer, 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 weak- 

 ened. 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, 

 afl'ord 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 vol- 

 canoes, 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 sur- 

 face, 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 



VOL. LVI. — 6 



