Revieivs — Asbestos. 421 



different grades are now on the market. Several otTier occurrences 

 are known in the Transvaal and Natal, but they do not seem to be of 

 much commercial importance. 



Y. — Asbestos. By P. A. Wagner. South African Journal of 

 Industries, November, 1917. 

 Tj"^OUIl principal varieties of asbestos are recognized, namely, 

 Jj chrysotile-asbestos, tremolite-asbestos, crocidotile-asbestos, and 

 iron-amphibole. All of these occur in South Africa, the first in 

 Rhodesia, the second in Zululand, the third in Griqu aland West, 

 and the last in the Transvaal. The reserves of chrysotile-asbestos in 

 Rhodesia and of crocidolite in Griqualand West are enormous, and 

 there seems to be every prospect of an important and flourishing 

 industry in the near future, likely to compete with Canada as the 

 world's greatest producer. 



VI. — The Zones or the Karroo System: and their Distribution. 

 By A. L. DU Toit. Proc. Geol. Soc. South Africa, 1918, 

 pp. xvii-xxxvi, with a map. 



FOR the subject of his presidential address to the Geological 

 Society of South Africa Dr. du Toit chose the general characters 

 and distribution of the rocks of the Karroo System. Sufficient work 

 has now been accomplished to allow of a discussion of the correlation 

 of the subdivisions of the system in different parts of the Union. 

 An important conclusion has been reached in the establishment of 

 a stratigraphical break between the Dwyka and Ecca Series, 

 beginning' somewhere between East London and Pondoland and 

 increasing in importance towards the north-east; this accounts for 

 certain anomalies seen in Natal and the Transvaal, where there is no 

 equivalent of the Upper Dwyka shales of the Cape Province. 

 Palaeontological study now tends to show that the Dwyka Series is 

 of Upper Carboniferous age, while the Ecca and Lower Beaufort 

 Beds are Permian, the Upper Beaufort, Molteno, and Red Beds are 

 Trias, while the uppermost volcanics may possibly be Rhgetic. The 

 author is to be congratulated on an excellent summary of a large 

 subject. 



R. H. R. 



Geologists' Association. 

 I. June 7, 1918.— J. F. N. Green, B.A., E.G.S., President, in the 



Chair. 



The following paper was read : — 



"The Skiddaw Granite: a Structural Study." By J. Frederick 

 N. Green, B.A., F.G.S. 



The problem of the age of the Skiddaw Granite can only be 

 attacked by structural methods. The distribution of cleavage in the 

 aureole points to pressure later than the intrusion. The Mosedale 

 fault, which brings unaltered parts of the Carrick Fell complex 

 against garnet-cordierite-horufelses of the inner aureole, is of the 



