RECENT ADVANCES IN SCIENCE 117 



tuffs. Intermediate and basic intrusions are also described. A 

 new type, hirnantite, is described, but the analysis given is at 

 variance with the mineralogical description, and the rock 

 appears to be an albite-keratophyre. 



W. N. Benson has described the petrology of the Devonian 

 igneous rocks of the Nundle district, New South Wales (Proc. 

 Linn. Soc. N.S.W. 191 5, 40, 121). The principal group is an 

 albite-rich keratophyre-spilite-dolerite series, similar to certain 

 pillow-lava series of Britain, and like them containing fine 

 pillow-form masses believed to have been formed by intrusion 

 into soft muds. A type called magnetite-keratophyre is believed 

 to be due to magmatic differentiation, assisted by pneumato- 

 lysis. The albite in these rocks is regarded as of primary 

 origin. 



A great series of pillow-lavas associated with thick chert 

 beds is described from the Kenai Peninsula, Alaska, by G. C. 

 Martin et alia {Bulletin 587, United States Geological Survey, 

 1 91 5). They are probably of Triassic age. 



Curious pyroxene-felspar dykes, consisting of orthoclase 

 and diopside, are found at Copper Mountain, Alaska {Pro- 

 fessional Paper 87, United States Geological Survey, 191 5, 40). 

 These vary widely in composition, ranging from 90 per cent, 

 orthoclase and 10 per cent, pyroxene, to 30 per cent, orthoclase 

 and 70 per cent, pyroxene. One of the orthoclase-rich varieties, 

 on analysis, is shown to have over 12 per cent, of potash, with 

 62 per cent, of silica, and falls into a new subrang, hettose, of 

 the American Quantitative Classification. 



Economic Geology. — The pressure of the war in increasing 

 the demand for certain minerals of economic importance has 

 led the Geological Survey to commence the publication of 

 special reports on the Mineral Resources of Great Britain. The 

 first three volumes are now to hand, dealing respectively with 

 Tungsten and Manganese Ores, Barytes and Witherite, Gypsum 

 and Anhydrite. The treatment is the same in each volume : 

 there is first an introduction dealing with the character, sources, 

 and uses of the minerals, followed by a detailed account of the 

 British occurrences and mines. 



Per Geijer in a paper on problems in iron-ore geology in 

 Sweden and America (Economic Geology, 191 5, 10, 299) makes 

 an instructive comparison between the metallogenetic provinces 

 of the United States and Sweden in which banded magnetite- 



