THE METAMORPHIC ROCKS OF ADELIE LAND. STILLWELL. 105 



resulted from the stress, and the mashing and granulitisation of the primary constituents 

 are absent. In this manner, then, the rocks of the Highlands of the Hudson in 

 North- Western New Jersey can be correlated with occurrences at Cape Denison and 

 in other parts of the world. 



The Assimilation Theory. 



The assimilation theory for the production of hornblende schist, biotite and horn- 

 blende gneisses, which has been illustrated in the preceding paper by Fenner, has had 

 wide application. It has been recently emphasised by Cole, who has quoted a large 

 number of references, and who considers that the undermining and weakening of the 

 earth's crust by molten magma is the only interpretation of the widespread phenomena.* 

 Cole states: " Again and again strongly banded gneisses occur in which granitic material 

 alternates with sheets of hornblendic or biotitic schist. The biotitic varieties can often 

 be traced back into amphibolites. In places lumps of these amphibolites are seen, 

 streaked out at their margins, and providing a clear explanation of the dark bands 

 throughout the gneiss. This swallowing up of a mantle of basic material by a very 

 different and highly siliceous magma rising from below is seen to be a world-wide 

 feature, wherever we find the lower crust-layers brought up within reach of observation." 

 Further on he continues : ' We see the highly metamorphosed material further 

 attacked by the great cauldrons under it and becoming seamed with intersected veins. 

 Block after block has been caught, as it were, in the act of foundering into the depths. 

 In the gradual absorption of these blocks, and their penetration by insidious streaks 

 of granite, we see pictured on a few square yards of surface the destruction of a conti- 

 nental floor." Such is the catastrophic manner in which the metamorphic phenomena 

 are accounted for by assimilationists. It needs to be pointed out that as soon as any 

 of the features are demonstrated to be the result of metamorphic action as opposed to 

 igneous action, the theory is rudely shaken. If another explanation, e.g., metamorphic 

 diffusion, be found for the supposed gradual assimilation, a modified statement becomes 

 necessary. If, further, some of the supposed invaded crust be actually shown to be 

 younger in age than the granitic magma, the theory must completely crumble unless 

 recast. The widespread nature of the evidence is no more than the widespread 

 occurrence of lithologically uniform areas of the crystalline schists. We must include 

 Cape Denison among such areas of crystalline schists, and there we find no reason to 

 appeal to molten magmas for explanation of the observed phenomena. 



Col*, Pre. Add, Sect. C.. B.A.A.S. Manchester, 1916. 



