Resume of Recent Scientific Publications. 465 



Gurich, Georg. " Zur Theorie der Diamantlagerstatten in Slid 

 afrika." Zeits. fair prakt. Geologie, Mai, 1897, pp. 145-8. 



The author deals with the dry diggings only, under the follow- 

 ing heads : (1) The cause of the form of the occurrence ; 

 (2) the origin of its contents ; and (3) the formation of the 

 diamond in particular. 



The shape and appearance presented by the pipes are dis- 

 cussed, and the "blue ground" described with regard to its 

 petrographical and mineralogical character. 



The views published by Cohen, Chaper, Lewis, Moulle, 

 Stelzner and others are briefly reviewed, and the author 

 supports Daubree's theory (which he confirmed by actual 

 experiments) that the pipes have been produced by powerful 

 explosions, making, however, a distinction between such as 

 have been filled by debris and such as have been pierced into 

 by ascending molten rock-material. The fragmentary nature 

 of the materials composing the blue ground speaks further, in 

 Dr. Giirich's opinion, for the correctness of the explosion theory. 

 The dykes which occasionally occur in the blue ground show 

 that intrusive action followed the original explosive infilling. 



With regard to the origin of the diamond, Dr. Gurich holds 

 that, as in Moissan's experiments, the carbon was held in the 

 basic magma as a metallic carbide and subsequently separated 

 out under high pressure as diamond. 



G. S. C. 



Garnier, Jules. " Gold and Diamonds in the Transvaal and the 

 Cape, being extracts from the Memoirs of La Societe des 

 Ingenieurs Civils de France," translated by C. de Sarigny. 

 Trans. Geol. Soc. South Africa, vol. hi., 1897, pp. 91-103, with 

 13 diagrams. 



Touches lightly on the geology of South Africa ; then goes 

 on to explain how beds of sand, &c, have been laid down on 

 inclines ; at the bottom of the great basins plastic mud con- 

 taining carbonaceous matter accumulates, and when the harder 

 beds deposited above become sufficiently thick, this mud is 

 pressed up through them. Where the mud contains carbon it 

 crystalises as diamantiferous blue ground ; where it is free from 

 carbon, the mud hardens to form dyke-rocks. 



E. H. L. S. 



