492 Sir J. B. Stone — The Kimherley Diamond Mines. 



Fig. 13.^ — From sicula side. 



Fig. 14. — From right side. The distal "wall of the right theca, not completely 

 developed, forms only a narrow band. Behind the apertural margin of 

 the right theca appears the projection of the sicula. In the interior 

 of the right theca and connecting canal the sicula appears to the left. 

 To the right, on the contrary, the canal is quite open. 



Fig. 15. — From anti-sicula side. 



Fig. 16. — From left side. The sicula appears here in the interior to the right, the 

 open connecting canal to the left. In the right aperture of the same 

 one gets a glimpse of the undeveloped distal wall of the right theca. 



11, — Notes on the Diamond-bearing Eock of Kimberlby, South 

 Africa. (I) By Sir J. B. Stone, M.P., F.GS. (II) By 

 Prof. T. G. BoNNEY, D.Sc, LL.D., F.E.S., and Miss C. A. 

 Eaisin, B.Sc. 



[At the end of last year, while on a visit to Sir J. B. Stone, I had 

 the opportunity of seeing a very interesting series of specimens from 

 the Kimherley mines, which he had obtained during a recent tour 

 in South Africa. Among these were two large lumps of the breccia 

 in which the diamond occurs. As these were in a much better con- 

 dition for microscopic examination than any which I had ever seen, 

 I asked him to let me study one of them. This request he kindly 

 granted, and sent me samples of all that he had collected. As not 

 very much has been written on the subject, at any rate in the 

 English language,^ the results of the investigation and the con- 

 clusions to which it has led may be worth publishing. At my 

 request, Sir J. B. Stone has contributed, notwithstanding his many 

 duties, a prefatory note on the mines and on the opinion which he 

 formed during his visit. — T. G. B.J 



(I) The KiMBERiiEY Diamond Mines, South Africa. 



By Sir J. B. Stone, M.P., F.G.S. 



TT may be fairly asserted that increased geological interest attaches 

 to the deeper workings of the Kimherley Diamond Mines as 

 they proceed. The remarkable development of underground mining, 

 following upon the amalgamation of interests, which was the out- , 

 come of the collapse of the surface workings in 1886, or thereabout, 

 has offered better opportunities for observation, not only of the 

 diamond matrix-material but also of the varying characteristics of 

 the neighbouring rock formations. 



The interest created among scientists, upon the first announce- 

 ment being made that the now famous diamond-bearing " Blue 

 Clay " filled up presumed necks of volcanic craters, has not faded 

 away, nor has the interest in the subject at all lessened. There is, 

 if anything, an increased desire to find out the secret workings of 

 Nature's laboratory, and to learn how the diamonds were formed, 



^ Reasons, in themselves very sad, have hitherto prevented the publication of the 

 elaborate investigations of the late Prof. Carvill Lewis, to which reference has been 

 made below. By a curious coincidence, his manuscripts and all the materials which 

 he had used were entrusted to me by Mrs. Carvill Lewis, just as I had completed my 

 share of the above paper. It is my intention to lose no time in preparing for 

 publication the work of my lamented friend. — T. G. B. 



