Reviews — Asbestos in the Union of South Africa. 185 



the retention of gases allowing these minerals to form, whereas 

 subaerial eruptions without water gave rise to augite. The volcanic 

 vents of the region appear to have been extremely persistent in their 

 localization, since the later basalts came from the same craters as 

 the andesites. 



This paper must be regarded as a valuable contribution to the 

 ever-growing American literature of the reef-problem and of the 

 petrography of the Pacific Islands. 



YI. — Asbestos in the Union of South Afkica. By A. L. Hall. 

 Geological Survey of the Union of South Africa, Memoir No. 12. 

 pp. 152, with 15 plates, 16 text-figures, and a map. Pretoria, 

 1918. Price 5*. 



OF late years the Union of South Africa has become an important 

 producer of asbestiform minerals for the world's market. It 

 possesses deposits of chrysotile, tremolite, and crocidolite, and a new 

 and important variety, here called amosite, has recently been 

 developed on a commercial scale ih the Transvaal. In this memoir 

 Mr. Hall gives a full account of the properties and occurrence of all 

 these varieties. Chrysotile is found in workable quantities in the 

 Carolina district of the Transvaal in the upper part of the Dolomite 

 Series, a few feet above a large basic sill. It also occurs in the 

 Tugela Yalley in Natal, as described by Dr. Hatch in 1910. 

 Crocidolite is found in very large quantities in the banded ironstones 

 of the Lower Griqua Town Series, which are equivalent to the lower 

 part of the Pretoria Series of the Transvaal. Amosite is an amphi- 

 bole, rich in ferrous iron and pale grey or nearly white in colour, 

 and remarkable for the great length of its fibres, which can be 

 obtained in quantity averaging 6 inches. It is found in the 

 Lydenburg and Pietersburg districts of the Transvaal, near the base 

 of" the Pretoria Series. The genesis of crocidolite and amosite is 

 discussed in detail and attributed to metamorphism of ferruginous 

 and siliceous sediments associated with rocks containing magnesia 

 and soda. The origin of the amosite deposits is believed to be 

 connected with the intrusion of the Bushveld complex. The 

 industrial aspects of the subject are also dealt with. 



YII. — On Sections in the Lower Permian Pocks at Claxheugh 



and Down Hill, Co. Durham. By David "Woolacott, D.Sc, 



P.G.S. Trans. Nat. Hist. Soc, Northumberland, Durham, etc., 



n.s., vol. v, pp. 155-162, with 4 plates and 2 figures, 1918. 



rriHE author discusses the various ways in which brecciation has 



JL been produced in the Permian rocks and describes sections 



showing that local disturbances have been produced by horizontal 



movements due to thrusting from west to east, by which part of the 



Marl Slate and Lower Limestone have been displaced and cut out. 



No suggestions are offered as to the cause of the thrusting, but 



reference is made to the work of Trechmann on deposits of anhydrite 



at Hartlepool and to the presence of sulphates in the Permian rocks 



of other parts of North-East England. It is suggested that the 



