186 Reports & Proceedings — Geological Society of London. 



removal of these by solution would at any rate lead to an accentuation 

 of the effects of such movements, if produced by otber agents. 



VIII. — Summary Report of the Mines Branch of the Department 

 of Mines, Canada, for the tkar 1917. 153 pp., with 

 4 figures. Ottawa, 1918. Price 15 cents. 



niHIS publication contains a summary of the work of the various 

 JL divisions of the Mines Branch and gives evidence of great 

 activity in several directions. Among the work of properly geo- 

 logical character may be mentioned reports on the iron-ores of the 

 Rainy River district, on the limestones of Ontario, and on certain 

 sands and sandstones. The Fuels and Fuel-testing Division in- 

 vestigated a large number of peat bogs in various localities, while 

 the Ore-Dressing and Metallurgical Division carried out tests on 

 a large number of ore samples, including gold, silver-lead, iron, 

 manganese, chromite, tungsten, and molybdenum. The Ceramic 

 Division examined into resources of clay and shale in several 

 provinces, and an account is given of the manufacture of magnesite 

 products, an industry of growing importance. 



EEPOETS -A-HSTID DPROCHEEJIDIIN-GrS- 



I. — Geological Society of London. 



February 5, 1919.— Mr. G. W. Lamplugh, F.R.S., President, in 



the Chair. 



The following communication was read — 



" The Geology of the Marble Delta, Natal." By Alexander Logie 

 DuToit, B.A., D.Sc, F.G.S. 



The paper deals with the crystalline dolomitic marbles of Port 

 Shepstone, Natal — rocks that have already been the subject of several 

 communications to the Society ; but its main object is to demonstrate 

 that certain "boulders" of alkali- granite, formerly regarded as 

 inclusions, are in reality parts of intrusive tongues, and to discuss 

 the mutual relations of the igneous rocks and the adjacent dolomites. 



The main area of Marbles covers a tract of about eight square miles. 

 It is not a solid block surrounded by granite and gneiss, but a bent 

 and twisted mass enveloped and underlain by igneous material, and 

 cut into several distinct portions by great intrusive sheets. 



The Marbles, almost wholly dolomitic in composition, are medium 

 to coarse-grained rocks that have their bedding-planes marked out by 

 various contact-minerals. They reach a total thickness of about 

 2,000 feet, and are divided into an upper and a lower portion by 

 a narrow belt of quartz-schist. 



The plutonic rocks are, for the greater part, coarse-grained biotite- 

 or hornblende-orthogneisses, with streaks and belts of hornblendic 

 gneisses, schists, and granulites at or near the contacts with the 

 Marbles. A conspicuous feature of the igneous rocks is that, for 

 a distance of two to eight miles from the contact, they contain red and 

 brown garnets. 



