566 SCIENCE PROGRESS 



tities of silica it has been found that those herbs which are 

 used by peasants in Middle Europe for the cure of tuberculosis 

 contain the largest quantity of silica. 



GEOLOGY. By G. W. Tyrrell, A.R.C.Sc, F.G.S., University, Glasgow. 



Economic Geology. — W. H. Emmons has published a revision 

 and amplification of his memoir on the enrichment of sulphide 

 ores under the more general title of " The Enrichment of Ore 

 Deposits " (U.S. Geol. Survey, 191 7, Bull. 625, pp. 530). 

 This is a most exhaustive treatment of the physics and chemistry 

 of the phenomenon of enrichment, which generally results from 

 the solution of ores near the surface and their reprecipitation 

 in depth. 



The stanniferous clays of the Kinta district (Perak), re- 

 garded by Scrivenor as of glacial origin and of Permo-Carboni- 

 ferous age, are now relegated by W. R. Jones (Q.J.G.S. 191 7, 

 72, pt. 3, 165-97) t0 a much later date, and are ascribed to 

 the weathering of a stanniferous granite, and of the adjacent 

 schists and phyllites. Ninety per cent, of the ore is derived 

 from mines situated near the junction of granite and country 

 rocks. On the contrary, in the Cooktown (Queensland) tin- 

 field, described by E. C. Saint-Smith (Queensland Geol. Survey, 

 Publ. No. 50, 1916, pp. 211) the recent alluvial deposits supply 

 by far the greater portion of the tin won, although there are 

 tin lodes connected with a granite that cuts the Gympie 

 (Permo-Carboniferous) formation. 



The great difficulties of arriving at the origin of the typical 

 West Australian gold deposit are well illustrated in two recent 

 memoirs (E. de C. Clarke, " The Geology and Ore Deposits 

 of Meekatharra, Murchison Goldfield," Geol. Survey of West 

 Australia, 191 6, Bull. No. 58, pp. 342 ; E. B. Feldtmann, 

 " The Geology and Ore Deposits of Kalgoorlie : Part 3, East 

 Coolgardie Goldfield," ibid. Bull. 69, 1916, pp. 152). The 

 rocks have been so intensely altered by ancient earth move- 

 ments that it is extremely difficult, if not impossible, to recog- 

 nise their original characters, or their relative ages and structural 

 relationships. The Coolgardie memoir is the third of a series 

 describing the famous Kalgoorlie field. The Moonta and 

 Wallaroo field (South Australia) is primarily a copper-mining 

 area (R. L. Jack, " The Geology of the Moonta and Wallaroo 



