CANADA. 333 



Logan in the Report of Progress for 184G-47 described the series on 

 the north shore of Lake Superior in ascending order, as follows {L c, 

 pp. 8-17):- 



" 1. Granite and syenite. 



"2. Gneiss. 



" 3. Cbloritic and partially talcose and conglomerate slates. 



" 4. Bluish slates or shales, interstratified with trap. 



" 5. Sandstones, limestones, indurated marls, and conglomerates, interstrati- 

 fied with trap. 



" Tlie rock at tlie hase of tlie series is a granite, frequently passing into a 

 syenite by the addition of hornblende, hut the hornblende does not appear to 



he often present wholly without the mica The granite appears to pass 



gradually into a gneiss, which seems to participate as often of a syenitic as a 



granitic quality The gneiss is succeeded by slates of a general exterior 



dark green colour, often dark-gray in fresh fractures, which at the hase appear 

 occasionally to be interstratified witli beds of a feldspathic quality, of the red- 

 dish color belonging to the subjacent granite and gneiss Some of the 



beds have the quality of a greenstone, others that of a mica slate, and a few 

 present the character of quartz rock. Rising in the series, these become inter- 

 stratified with beds of a slaty character, holding a sufficient number of pebbles 

 of various kinds to constitute conglomerates. The pebbles seem to be of 



various qualities, but apparently all derived from hypogene rocks The 



formations which succeed, rest unconformablj' upon those already mentioned. 

 The base of the lower one [No. 4], where seen in Thunder Bay in contact with 

 the subjacent green slates, presents conglomerate beds probably of no great 

 thickness, composed of quartz pebbles chiefly, with a few of red jas])er, and 

 some of slate in a green arenaceous matrix, consisting of the same materials in 

 a finer condition." 



Reposing on the bluish slates (No. 4) are "sandstones, limestones, 

 indurated marls and conglomerates interstratified with trap," and 

 crowned by an enormous amount of volcanic overflow. No evidence 

 is adduced to show that these two " volcanic formations " are uncon- 

 formable with each other, but sufficient proof is cited to show that they 

 are tin conformable with the granite, gneiss, and chlorite slate. Tlie 

 volcanic formations are, however, regarded as being older than the 

 Potsdam sandstone. (I. c, p. 34.) 



Logan further remarks : — 



" The cbloritic slates at the summit of the older rocks on which the volcanic 

 formations rest nnconformably, bear a strong resemblance to those met ■«-ith in 

 the upper part of Lake Temiscamang on the Ottawa, and it appears probable 

 they will be found identical." (I. c, p. 34.) 



