RECENT ADVANCES IN SCIENCE 375 



land, Iceland, and the Faroes, are much Jficher in TiO» than the 

 areas respectively north and south of it. The paper concludes 

 with a short but valuable discussion of the conception of 

 petrographic provinces. 



Balsillie, D., On a Hypersthene Andesite from Pitcullo, 

 Fife, Geol. Mag. 191 8, 5, 346-50. 



Bartrum, J. A., Additional Facts concerning the Distribu- 

 tion of Igneous Rocks in New Zealand, Trans. N.Z. Inst. 191 7, 

 49, 418-24. 



Grout, F. F., The Pegmatites of the Duluth Gabbro, Econ. 

 Geol. 191 8, 13, 185-97. 



" Lopolith " is a term suggested by F. F. Grout for an 

 igneous form exemplified by the Duluth gabbro, the Sudbury 

 nickel intrusive, the Bushveldt complex (and probably also 

 the Insizwa mass elsewhere mentioned) (Amer. Journ. Sci. 191 8, 

 46, 516-22). It is defined as a large, lenticular, centrally- 

 sunken, generally concordant, intrusive mass, with a thickness 

 approximately one-tenth to one-twentieth of its width or 

 diameter. The type differs widely from a laccolith, with which 

 it has generally been classed, both in form and in its mechanics 

 of intrusion. 



In a discussion of the internal structures of igneous rocks, 

 F. F. Grout {Journ. Geol. 191 8, 26, 439-58) comes to the con- 

 clusion that banding and related fluxion-structures probably 

 develop during crystallisation, while the magma is in convec- 

 tion-circulation. The author cogently criticises the current 

 suggestions of movements of intrusion or deformation for the 

 origin of parallel, alternating, mineralogically-unlike bands. 



Economic Geology. — Ore-Deposits and Igneous Magmas. — 

 The subject of the direct relation of ore deposits to igneous 

 magmas has been much discussed of late, as shown by the large 

 number of contributions to the study of the Sudbury nickel 

 intrusive (see Science Progress, April 191 8, p. 567, and 

 present article). Among British authors W. H. Goodchild has 

 recently made some notable studies of the general problem. 

 He has just published a paper on " The Evolution of Ore- 

 Deposits from Igneous Magmas " (Mining Mag. 191 8, 18, 20-9 ; 

 75-82; 131-41; 186-94; 240-9; 296-306; 19,21-32; 78-88; 

 135-44 ; 188-99), which is really a long and elaborate petro- 

 logical treatise, shortly to appear in book form. This work is 

 deserving of a much more extended notice than can be given 



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