27 



dyke where crossed by a line of shearing. In the case of 

 these Canadian dykes, however, the amphilbolite is not 

 confined to that portion which has been clearly subjected to 

 movement, but forms the whole mass of the dyke. 



(c) Amphibolites which are identical in physical 

 character and in composition with those described under 

 (b) are also produced by the metamorphic action exerted 

 by the granite-batholiths on the limestones through which 

 they cut. This is a remarkable fact, and one which at 

 first sight seems scarcely credible. It is, however, a 

 change which has undoubtedly taken place on a large scale. 



In addition to the amphibolites which have originated 

 in the three ways above mentioned, it is highly probable, 

 judging from their character and mode of occurrence, 

 that the amphibolite bands associated with the large 

 gabbro and diorite masses — as, for instance, that running 

 in a north-easterly and south-westerly direction through 

 the township of Wollaston, and that extending from the 

 south-eastern portion of the township of Cardiff, into 

 Anstruther — represent highly altered basic volcanic ashes 

 and lava-flows, connected with vents represented by the 

 gabbro-stocks. The latter of these amphibolite bands 

 presents a great variation from place to place in the char- 

 acter of the constituent rock. While in some places it is 

 well banded, elsewhere it is streaked or presents an appear- 

 ance strongly resembling flow-structure, with lighter colour- 

 ed lath-like forms highly suggestive of feldspar phenocrysts 

 thickly scattered through it. Yet elsewhere the appearance 

 suggests an original amygdaloidal structure. The rock, 

 however, is so completely recrystallized, that a micro- 

 scopic examination does not yield any conclusive evidence 

 concerning its original character. 



IV. Gabbros and Diorites. 



These rocks differ from the amphibolites in that they 

 are massive and usually coarse grained. They also differ 

 in their mode of occurrence as great basic intrusions. 

 While some of these intrusions are pretty uniform in 

 character, others display a very marked differentiation 

 and present many petrographical varieties within a single 

 intruded mass. 



Many of them, in addition to pyroxene, a basic plag- 

 ioclase and iron ore, hold a large amount of hornblende 



