liY H. I. JENSEN. 533 



schist, glaucophane-albite-epidote schist, or sericite-glaucophane 

 schist or jadeite. This fact alone to a great extent helps to 

 .prove that their intrusion was subsequent to the production of 

 schistosity in the surrounding rocks. A faint schistose parting 

 in the border facies is only the result of flow and pressure in 

 cooling 



All these points do, in my opinion, offer very suggestive 

 evidence for the theory here suggested as to the origin of the 

 foyaitic magma; and to Griibenmann's excellent work I feel 

 grateful for greatly helping to clear my mind on the subject of 

 crystalline schists. 



The " deepest zone" of crystalline schist-formation (Griiben- 

 mann) corresponds to the zone of shear of van Hise, or the zone 

 of " rock-flowage " of American authors generally. In this zone 

 the most readily liquefiable rocks would naturally first be squeezed 

 away laterally on the accumulation of sediment above. The 

 shear zone rises closest to the surface under the continents (see 

 Chamberlin & Salisbury, "Geology," Vol.ii.), hence here we have 

 most opportunity of finding alkaline magmas exposed by denuda- 

 tion or expelled to the surface. Under the raised ocean-basins 

 which now form the Alps and the Himalayas (the Mediterranee 

 Centrale and Tethys), if not squeezed away laterally they exist 

 only so deep as not to be exposed to the surface by denudation. 



It must again be emphasised that a belt of alkaline rocks often 

 occurs, in fact generally occurs, between an area of highly meta- 

 morphic rocks of the fundamental complex with Eopalseozoic and 

 an area over which these same rocks are capped with almost 

 horizontally bedded Mesozoic rocks. This suggests that the 

 alkaline line is the fracture-line between an elevated and a sub- 

 sided segment of the earth's crust. The alternate sedimentation 

 on one side or other of the line is an expression of the statement 

 of Suess that the Riickland of one cycle frequently becomes the 

 Yorland of the succeeding cycle, sometimes the one, sometimes 

 the other segment being draw r n down at the faster rate. 



In the intense folding of the Archaean and Eopalaaozoic rocks 

 in the neighbourhood of alkaline areas and the horizon tality of 



