As Indicating a Sedimentary Origin. 353 



been exposed to regional pressure, there is produced a rough paral- 

 lelism amongst the fragments, and this enhances the sedimentary 

 appearance. 



"3. Special Facts from the Cortland Begion." — I shall confine 

 myself to the essential points, omitting those which, though not 

 irrelevant, would count for little if my main contentions are sustained. 



Some interesting contact-phenomena are seen near Cruger's Point 

 (p. 114). The mica-schist towards the north comes to an end against 

 soda-granite and quartz-diorite. Approaching the igneous rocks, 

 the schist " becomes increasingly staurolitic and garnetiferous, and 

 passes in places into a true gneiss." Par* passu with this mineral 

 change, the schist becomes more and more contorted, and is " inter- 

 laminated with nodose-lines of quartz, vein-like in origin." At 

 the junction, " the schist is mostly a garnet rock containing much 

 fibrolite and staurolite, and the latter is in some places granular- 

 massive in a small way. Just below the granite, the layers are a 

 compact body of flexures, and in the soda-granite ^ there is another 

 flexed layer rather faintly indicated." 



Assuming the accuracy of Prof. Dana's data, which I am doing 

 throughout this paper, I find myself unable to accept his inferences. 

 He considers that the phenomena just described confirm his theory ; 

 but, with deference to the opinion of so eminent a scientist, I venture 

 to maintain that they more justly fit the theory of intrusion. It is 

 not unusual for schists to undergo increased contortion at the contact 

 with a large intrusive mass. I have described cases of this in my 

 paper on Donegal.' This fact suits me quite as well as Prof. Dana. 

 The production of secondary minerals I have also noticed at and 

 near the contact of granite and schist (lac, cit.). The composition of 

 these minerals would of course depend upon the composition of the 

 surrounding masses, but at Dunlewy one of the contact-minerals 

 was " allied to kyanite," and therefore not far removed from stauro- 

 lite. Heated waters, soaking through granite or schist, could hardly 

 fail to give rise to chemical changes in the other rock, and these would 

 under favourable conditions reach to a considerable distance from 

 the line of contact. Mica-schist could obviously cause little change 

 in other rocks ; but the felspar and hornblende in the granite and 

 diorite would readily furnish materials for the production of such 

 minerals as kyanite, staurolite, and some garnets. The abundance 

 of quartz-veins tells strongly in favour of my view, the silica set 

 free in the genesis of the basic minerals being redeposited. 



The "flexed layer rather faintly indicated" demands special atten- 

 tion. According to Prof. Dana, it is a bed which originally "approached 

 somewhat the granite in character, but which, owing to the nature 

 of its material, was not wholly obliterated." To the enquiry whether 

 such masses may have been fragments of schist entangled in the 

 granite, Prof. Dana replies that " they lie so conformably to the 

 flexures of the " main body of " schist as to suggest a negative reply." 

 He rightly attaches great importance to this parallelism of strike, 



1 The italics are Professor Dana's. 



2 Quart. Journ. Geol. Soc, May, 1885, pp. 225, 226. 



D£CADB III. — VOL. IV. — NO. Till. 23 



