RECENT ADVANCES IN SCIENCE 281 



Arenig to the Glenkiln is exposed. Contemporaneous igneous 

 rocks appear in the Tetragraptus shales and in the Dicrano- 

 graptus bifidus beds. Prof. O. T. Jones and W. J. Pugh describe 

 the geology of the district around Machynlleth and the Llyfnant 

 valley {ibid. 343). The rocks here range from the Hartfell to 

 the Valentian, and are arranged in large corrugated folds which 

 are accompanied by strike-faults parallel to the axes of folding. 



An outline of the geology of Prince Charles Foreland, 

 Spitzbergen, is given by R. M. Craig [Trans, Edinburgh Geol. 

 Soc. 1 91 6, 10, 276). He describes folded grits and quartzites of 

 Silurian age, a coarse conglomerate probably of Devonian age 

 very like some of the Old Red Sandstone conglomerates of 

 Scotland, and Tertiary sandstones and shales the age of which 

 was determined by plant remains collected by Dr. W. S. Bruce. 



C. R. Stauffer publishes a detailed memoir on the Devonian 

 of South-western Ontario (Memoir 34, Geological Survey of 

 Canada, 191 5, 341 pp.). It is mainly a richly fossiliferous lime- 

 stone formation, yielding important economic products such 

 as petroleum and gas, building stones, and lime for Portland 

 cement. 



The study of Cordilleran geology is furthered by yet another 

 memoir, " The Geology and Ore-deposits of Rossland, British 

 Columbia," by C. W. Drysdale (Memoir jj, Geological Survey of 

 Canada, 191 5, 317 pp.). The oldest formation is believed to be 

 Carboniferous, but the bulk of the area is occupied by igneous 

 rocks of Jurassic and Tertiary age which are associated with 

 two main periods of mineralisation. 



Petrology. — By means of volumetric and chemical analyses, 

 aided by determinations of density and grain, A. C. Lane has 

 demonstrated gravitative differentiation in an extrusive Triassic 

 basalt from Nova Scotia (Trans. Amer. Inst. Min. Eng. February 

 IQI 6, 535). There is a concentration of felsic constituents 

 toward the top of the flow and of mafic constituents towards 

 the base. This result is in accordance with recent experiments 

 by Bowen and Anderson on artificial melts. 



The pitchstones of Mull are described by E. M. Anderson 

 and E. G. Radley (Quart. Journ. Geol. Soc. 1916, 71, 205). 

 They are divided into porphyritic and non-porphyritic types 

 respectively, which, with their stony equivalents, are classed as 

 two new types of rocks, leidleite and inninmorite. The boundary 

 between crystalline and glassy facies is very sharp, and devitri- 



