Geology. 369 



The Swan Coastal Plain has experienced three stages : downfault- 

 ing which submerged the area and permitted the deposition of 

 river-borne material on the sea floor ; a widespread uplift which 

 restored the sea floor to the land ; and a later slight uplift still in 

 progress. An interesting physiographic feature is the fresh Darl- 

 ing fault scarp not appreciably modified by stream dissection. 



Bull. 49, Geology and Mineral Resources of the Yilgarn Gold 

 Field. Part I, Southern Cross, by E. C. Saint-Smith and R. A. 

 Farquharson, 1913. Pp. 193/ 10 pis., 52 figs. This report 

 deals exclusively with the Southern Cross Mining center, and is 

 the first of a series designed to cover the Yilgarn Gold Field. 

 Petrology and economic geology, including microscopic and 

 chemical analyses, are given the chief attention. h. e. g. 



7. Geology of the Titanium and Apatite Deposits of Vir- 

 ginia y by Thomas L. Watson and Stephen Taber; Virginia 

 Geol. Sur. Bull. III-A; 1913. Pp. 308; 37 pis., 22 figs.— The 

 districts here described lie in Amherst-Nelson, Roanoke, and 

 Goochland-Hanover counties. The rocks of the Amherst- 

 Nelson area have close genetic relationships and are all charac- 

 terized by the presence of apatite and the titanium minerals, 

 rutile and ilmenite. They consist of monzonite-gneiss, syenite, 

 gabbro, diabase and the rock called nelsonite made up chiefly of 

 apatite with ilmenite, rutile or magnetite. They are all intrusive 

 and holocrystalline in texture. Gradations occur between the 

 gabbro and the syenite and the gabbro and nelsonite. The nel- 

 sonite occurs in the form of dikes varying in length of strike up 

 to 2000 feet and in width up to 65 feet. These dikes vary con- 

 siderably in the proportions of the different minerals present, all 

 of which at times become dominant in amount. The rutile 

 deposits in this district were first mined in 1902. 



In general the geology of the Roanoke area is similar to that 

 described above. Similar dikes of nelsonite occur in syenite and 

 pegmatite. The rocks have suffered intense metamorphism. 

 There are some striking differences in the secondary minerals of 

 the two districts. 



The Goochland-Hanover area shows a different series of rocks. 

 The chief types are a granitic gneiss cut by granitic pegmatite 

 and a variety of basic igneous rocks. The rutile occurs in the 

 pegmatites. The surface rocks in all these areas are badly 

 weathered. w, e. f. 



III. Miscellaneous Scientific Intelligence. 



1. Conferences de Radiumbiologie, faites d V TIniversite de 

 Gand en 1913 ; par MM. Jacques Danne, Paul Giraud, Henri 

 Coutard, Gaston Danne. Pp. 214. Brussels, 1914 (L. Severeyns, 

 34 rue Botanique). — This set of lectures delivered by specialists 

 in radioactivity cannot fail to be of value to those interested in 

 the application of radium in the field of medicine. The authors 

 are all connected with the Laboratory of Radioactivity at Gif. 



