258 abstracts: geology 



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The iodine number of the raw oil was 179.6. The greatest decrease 

 (to 171.6) was caused by kaolin. Flake graphite, artificial graphite, 

 zinc chromate, zinc oxide, and chromium oxide had practically no 

 effect, and basic carbonate of lead, Indian red, magnetic black, and 

 lead chromate had but a very sHght effect. The percentage of ash in 

 the raw oil (0.13 per cent) was raised to 0.40 per cent by the basic car- 

 bonate of lead. The increases due to the other pigments were but 

 slight. Basic carbonate of lead, kaolin, and lead chromate bleached the 

 oil. The results as a whole show surprisingly small changes due to the 

 pigments. At the end of two years the results obtained were prac- 

 tically the same as those obtained at the end of one year. In no case 

 was the iodine number lowered to a figure below that given by pure 

 raw oil from South American seed (171). The percentage of manganese 

 in sixteen samples of raw linseed oil of known purity and source varied 

 from a faint trace (less than 0.0002 per cent) to 0.0008 per cent. 



E. W. B. 



GEOLOGY. — The Eagle River region, southeastern Alaska. Adolf 

 Knopf. Bulletin U. S. Geological Survey No. 502. Pp. 61, with 

 maps, sections, and illustrations. 1912. 



The Eagle River region. Id eludes the northern portion of the Juneau 

 gold belt, extending northwestward from Salmon Creek, near Juneau, 

 to Berners Bay. This strip of territory is 32 miles long and embraces 

 approximately a third of the entire length of the gold belt. 



The rocks are arranged in belts that strike parallel to the general 

 trend of the gold belt and dip steeply northeast. The general parallelism 

 of stratification, cleavage, schistosity, gneissic foliation, dikes, and ore 

 bodies is the salient geologic feature of the region. 



The larger part of the gold belt is underlain by an interstratified series 

 of slates and graywackes, with some conglomerates. This assemblage of 

 sedimentary rocks, together with intercalated masses of volcanic rocks, 

 has been named the Berners formation. Fossil plants, consisting chiefly 

 of ferns, indicate that it is of Jurassic or Lower Cretaceous age. 



The volcanic rocks, associated with the slates and graywackes consist 

 of lavas, flow breccias, tuffs and coarse breccias, conglomerates, and 

 various kinds of mixed rocks. The clastic material far exceeds the mas- 

 sive rock in bulk. The lavas are in many places extremely amygdaloidal 

 and locally display a striking ellipsoidal structure. They are character- 

 ized by the widespread prevalence of numerous well-formed and well- 

 preserved phenocrysts of augite embedded in a dense-grained matrix of 



