Revieivs — Mineral Resources of the British Emjyire. 179 



curious basin of dolomite on Vogelstruisfontein, south of Roodepoort. 

 It is considered tbat the Elsburg beds are perfectly conformable to 

 the Upper Witwatersrand series, but indicate a gradual overlap 

 of the last-named over the Lower Witwatersrand. The name of 

 Transvaal System for the Black Reef-Dolomite-Pretoria series must 

 now be regarded as standardized, in place of Potchefstroom System 

 formerly used by Hatch and Corstorphine, but there appears to 

 be no particular reason for its adoption. 



The memoir gives an admirably clear account of the physiography 

 and geology of this interesting and important area, bringing out all 

 the salient features. Only one page is devoted to the gold-reefs, and 

 the general geological reader unacquainted with the district would 

 not acquire a very clear idea of their features and extent. There is 

 singularly little reference to the highly important East Rand area, 

 which lies just on the eastern margin of the map. 



The memoir concludes with an excellent chapter by Dr. du Toit 

 on the underground sources of water-supply in the Dolomite. 



R. PI. R. 



Imperial Institute : Monographs on Mineral Resources 

 WITH Special Reference to the British Empire : Oil- 

 Shales. By H. B. Cronshaw, B.A., Ph.D. pp. x + 80. 

 London: John Murray. 1921. Price 5s. net. 



rpHIS volume is a companion to the recent memoir on petroleum by 

 -*- the same author, and it combines that lucidity of exposition 

 with summary treatment characteristic of the earlier work. Latterly 

 public interest has been directed to the problems facing an increased 

 demand for and decreased supply of natural petroleum, and while the 

 ultimate location and opening up of new oilfields must necessarily 

 form one of the chief solutions, mitigating circumstances will also 

 be found in the development of the world's oil shale resources, which 

 may, without exaggeration, be regarded as prodigious. In America 

 the possibilities of the oil shale industry have long been recognized 

 though little progress seems to have been made, while in this country, 

 although in the Midlothian occurrences we recognize the pioneer 

 field, comparatively little heed had been paid to its development 

 until the war caused a focus of attention on national resources. 

 In 1920 the American industry received an impetus from the 

 researches and publications emanating from the Colorado School 

 of Mines, and Alderson's well-known " Oil Shale Industry " created 

 a favourable atmosphere for a wider consideration of the possibilities 

 of oil production from shales and torbanites. A statement of the 

 world's resources of such raw material was the natural sequel to 

 this, and the publication of the present memoir is therefore a further 

 step in the right direction. 



The sources of supply of oil shale are dealt with under the headings 

 of British Empire and Foreign countries ; the former comprises 

 the occurrences in the British Isles, South Africa, Canada, and 



