L78 \. i . i w\ son — i;i:i. itioxs of the lrcheax of caxada. 



tioned. In the A.rchean, rocks of this and more pronounced micaceous 

 character to true mica schists are traceable into clay slates and Biliceous 

 clastic rocks with unobscured original characters. Other mica schists arc 

 dircctlv traceable into conglomerates and agglomerates, and appear to be 

 but excessively squeezed facies of these rocks where the conglomeratic or 

 agglomeratic characters have been obliterated and much mica developed. 

 Ami in -nine mica schists, where no direct transition can be established, tra< 

 of conglomeratic structure can occasionally be detected. The mosl distinct ly 

 crystalline of these mica schists are entirely comparable with the mica schists 

 of the Bergen peninsula in Norway, where Reusch a few year- ago found 

 beautiful Silurian fossils,* some of which the writer has himself more recently 

 collected under the guidance of that distinguished geologist. 



Many mica Bchists of the Ontarian system arc, further, entirely similar to 

 the " hornfels " or crystalline schists of the contact zones of various post- 

 Ajrchean granitic irruptions, which are undoubtedly the altered facies of 

 normal sediments. Some of the feldspathic mica schists, of a fine-grained, 



thinly laminated aspect, < imonly called gneisses, are in parts of the 



Ontarian system traceable into quartz-porphyries of the same normal 



character a> those which constitute the vulcanic portions of many Paleozoic 

 -eric.-. The researches of Lehmann f have established Buch transformations 

 as tacts, the explanation of which, as demonstrated by thai eminent investi- 

 gator and now generally accepted, is found in the deformation of the rock by 

 pressure and in the chemical activity induced thereby. For the mosl part, 

 however, the feldspathic mica schists, such as are abundant in the Coutchich- 

 ing group, are, like the non-feldspathic mica Bchists associated with them, 

 very probably of metamorphic derivation from normal Bediments. 



In port inns of these format ion- the writer has recently detected vestiges of 

 conglomeratic structure. In places they pass into rocks that are little more 

 than slightly micaceous quartzites, and their distinct bedding and regular 

 stratigraphy are those of sedimentary rock- as contrasted with the lenticular 

 arrangements which obtain in volcanic accumulations. Their contact phe- 

 nomena against the granites and granite-gneisses of the Laurentian are 

 identical, so tar as Btudied, with intrusive granites, particularly in the 



development ofandalusite crystals. They corresp I closely in lithological 



character and in the nature of their relation- in the Laurentian with the 

 descriptions given usby Barrois : of the feldspathic mica schists of Cambrian 

 . which in Brittany are pierced and altered by great irruptions of granu- 

 li t > - tin- true granite, or granite with two micas, of the Germans), which 

 rock forms very extensive portions of the Laurentian northwest of Lake 

 Superior. 



. ii 



II, ime : 



