356 SCIENCE PROGRESS 



that have arisen at various dates by the intrusion of igneous 

 rock into sediments or schists. Perhaps a reference should be 

 given here to Lawson's J famous evidence of the absorption of 

 Huronian rocks by the so-called Laurentian, or fundamental 

 gneiss, at Rainy Lake. J. W. Gregory, 2 to quote an extreme 

 case, has written of the gneisses of the Cottian Alps : " Para- 

 doxical though it may appear, the evidence renders it most 

 probable that the Waldensian gneiss, instead of being of 

 Laurentian age, is really Pliocene, and, with the exception of 

 the Saharian and recent alluvium and the glacial moraines, is 

 the newest rock in the Cottians." 



Harker, 3 again, has given us an example, admirably studied 

 in the field, of the formation of gneiss in Tertiary times in the 

 Isle of Rum. Before referring to this in detail, we should note 

 that Callaway, 4 as far back as 1887, the year in which Levy 

 published his paper, " Sur l'origine des terrains cristallins 

 primitifs," showed how gneiss has arisen in Co. Galway by 

 the intrusion of granite into rocks rich in hornblende. The 

 latter underwent partial melting and streaking out, and the 

 resulting banded crystalline rock is thus of composite origin. 

 In 1893, 5 again, Callaway, while dwelling strongly on the 

 influence of pressure-metamorphism, cited a number of gneisses 

 produced by injection of igneous rocks among the ancient 

 masses of the Malvern Hills. A. Geikie and Teall, 6 in dealing 

 with handsomely banded gneisses of igneous origin among the 

 Tertiary rocks of Skye, have presumed that a separation of 

 material, on the one hand more rich in silica and on the other 

 more basic, took place in the plutonic caldron underground, and 

 that the two types of magma moved forward together in a 

 streaky viscid flow. But there are abundant cases where strong 



1 Ann. Report Geo/. Surv. Canada for 1887, p. 133 F. Cf. Geikie on 

 enclosures in the Hebridean gneiss of Loch Carron, Ancient Volcanoes, vol. i. 



p. 117. 



2 "The Waldensian Gneisses," Quart. Joum. Geol. Soc. London, vol. 1. (1894), 

 p. 232. 



3 " The Overthrust Torridonian Rocks of the Isle of Rum, and the Associated 

 Gneisses," ibid., vol. lix. (1903), pp. 189-215. Especially pp. 201-13. 



4 "Alleged Conversion of Crystalline Schists into Igneous Rocks in Co. 

 Galway," Quart. Joum. Geol. Soc. London, vol. xliii. (1887), pp. 521, 523. 



5 Ibid. vol. xlix. p. 413. 



6 " On the banded structure of some Tertiary Gabbros in the Isle of Skye, : ' 

 Quart. Joum. Geol. Soc, vol. 1. (1894), p. 656. Also Geikie, Ancient Volcanoes oj 

 Great Britain, vol. ii. p. 342, etc. 



