Reviews — Swedish Archcean Structures. 133 



X. — Swedish Aech^an Structures and their Meaning. By P. J. 

 Holmquist. Bull. Geol. lust. Univ. Upsala, vol. xv, pp. 125-48, 

 1916. 



FROM the evidence brought forward in this paper the following 

 sequence of events seems probable : the porphyry-leptite rocks 

 are the oldest known formation ; they represent ashy volcanic 

 deposits, comparable to the Keewatin. These sank in blocks into 

 the underlying granite magma, being metamorphosed and partly 

 assimilated. After the consolidation of this granite magma the 

 whole was affected by dynamometamorphism, forming different 

 varieties of gneissose and schistose rocks of varying grades of 

 alteration, the highest grades of metaniorphism being closely 

 connected with pegmatitization. The latest eruptive masses of the 

 Archaean consist of very acid granites, pegmatites, and aplites. 



XI. — Department of Mines, Canada, Summary Report, 1917. 

 Part B. 48 pages, with 1 text-figure. Ottawa, 1918. 



11HIS instalment of the Summary Report for 1917 contains accounts 

 of geological reconnaissances and surveys in various parts of 

 British Columbia and the Yukon Territory. Most of the areas dealt 

 with contain minerals of economic value, especially gold, and mining 

 is now being developed to a considerable extent. Most of the 

 mineralization is evidently due to the intrusion in Jurassic and early 

 Cretaceous times of the great igneous masses known collectively as 

 the " Coast Batholith ". More detailed work has shown the existence 

 in many places of portions of the original sedimentary roof of this 

 batholith in regions formerly considered to be entirely occupied by 

 igneous rocks. This is of much importance, since most of the ores 

 occur as contact deposits at the junction of the batholith with the 

 older rocks. 



IREIPOIEtTS J^ISTID PEOCEEDinSTGS. 



I. — Geological Society of London. 

 1. January 8, 1919.— Mr. G. "W. Lamplugh, F.R.S., President, in 



the Chair. 



The following communications were read : — 



(1) "On 'Wash-outs' in Coal-seams and the Effects of Con- 

 temporary Earthquakes." By Percy Ery Kendall, M.Sc, E.G.S., 

 Professor of Geology in the University of Leeds. 



The author differentiates two types of interruptions in coal- 

 seams which have been confused under the geueral term of "wash- 

 outs", "wants", "nips", or "dumb-faults". One type he believes 

 to be due, as geological writers have mostly held, to erosion by 

 contemporary or sub-contemporary streams which coursed through 

 the alluvial area where the coal-material was accumulating as a 

 species of peat. The channel thus cut was subsequently infilled 

 with sedimentary materials. 



He describes a number of examples of this type in the Midland 

 Coalfield, some being sinuous in course and traceable over many 



