140 proceedings: geological society 



of its course ; and that large rivers generally in high latitudes, especially 

 those of northern Siberia, should have characteristics similar to those 

 of the Yukon. 



The first authentic data regarding the Siberian rivers has just be- 

 come available in Nansen's new book, Siberia the Land of the Future, 

 and both the data and the author's interpretations are in entire har- 

 mony with the conclusions cited in the earlier paper by the speaker. 



Discussion. S. R. Capps and F. C. Schrader expressed the opinion 

 that, as regards the Yukon and Tanana, other factors than the earth's 

 rotation were of much importance. Such, for instance, was the for- 

 mation of delta deposits in streams entering from one side and not 

 from the other. Eakin agreed that this was a factor of importance 

 but did not beheve the whole effect could be ascribed to it. 



E. W. Shaw, A unique coal mine gas explosion. At the time of the 

 unprecedented high water on the lower Ohio, in the spring of 1913, a 

 gas explosion occurred in a coal mine at Equality, Illinois, which was 

 unique in that the gas was ordinary air. As the water approached the 

 mine efforts were made to prevent ingress by throwing up a low dike 

 about the shaft, but when this dike had been raised to a height of about 

 5 feet the water broke through and rushed down the. shaft. The space 

 in the mine once occupied by the milhons of cubic feet of coal which 

 had been mined out was at this time occupied by air, and the water 

 rushed down in such volumes that it allowed no air to escape. After 

 several hours the reaction came with a roar. The water bounced out 

 again, geyser fashion, bringing with it all manner of debris, coal cars, 

 tools, etc., and throwing them high in the air. Perhaps the most 

 important fact concerning this remarkable occurrence is that the 

 owners of this mine, like most coal operators, had no map of their 

 workings, and the site chosen for a new shaft was not sufficiently 

 distant to avoid breaking through into the old mine. An expenditure 

 of thousands of dollars was necessary to pump the water out so that 

 the new shaft could be used. 



« 



REGULAR PROGRAM 



Olaf Andersen, Mineral occurrences and associations in southern 

 Norway. The granitic pegmatite dikes form large bodies injected into 

 various types of pre-Cambrian rocks. The dikes are, as a rule, very 

 coarse-grained, some of the minerals (e.g., feldspars) forming huge 

 crystals. Graphic granites and various other graphic intergrowths 

 are very common. The main feldspar is always a microcline perthite. 

 Plagioclases (commonly oligoclase) are also present in considerable 

 quantities. Micas (biotite and muscovite) are found in most of the 

 dikes. Magnetite is commonly present in small amounts. With 

 respect to the associations of the less common minerals several types 

 may be distinguished: the beryl-bearing dikes, the tourmaline-bearing 

 dikes, the dikes rich in niobates and tantalates, etc. Each type has its 

 characteristic mineral association, but there are no sharp boundaries 

 between the types. 



