©4 PKOCEEDINGS OF THE GEOLOGICAL SOCIETY. 



This is followed, after an interval, by another rock, in aspect more 

 like a schistose dark quartzite, but which, under the microscope, 

 does not materially differ from the last. Nearer Sudbury the rocks 

 resemble dull-coloured quartzites; they contain many fragments, 

 subangular in form, often small, but occasionally as much as two 

 inches in diameter, of a grey granitoid rock. On microscopic exa- 

 mination the matrix seems rather more altered than its macroscopic 

 aspect suggests *, and this also is the case with the quartzites and 

 quartzose fragmented rocks a little beyond Sudbury, amongst 

 which Dr. Selwyn showed me some extraordinary breccias. The 

 matrix of these also exhibits, under the microscope, more minera- 

 lization than I should have expected. Between Sudbury and 

 Pagamasing I traversed rocks mainly assigned to the Huronianf, but 

 if I mistake not, the Laurentian series reappears more than once, 

 and there are occasionally bosses of granite and syenite, probably 

 of very ancient date, as they show signs of crushing. In the Huro- 

 nian series, we passed various quartzites, some very conglomeratic. 

 These, I believe, are considered probably to represent the well- 

 known Huronian quartzite with pebbles of red jasper (which I did 

 not see). There appeared to be slaty rocks, but as two, which, in the 

 field, I thought more probably schistose slates, prove to be fine- 

 grained hornblende-schists modified by subsequent pressure, I do 

 not like to speak with certainty. I obtained, however, a specimen of 

 an indurated volcanic ash and one of a slaty grit, which seems to be 

 nearly in the same mineral condition as those in the Welsh 

 Cambrian series. These Huronian rocks, together with the igneous 

 bosses, appear to have been much more affected by subsequent 

 pressure than the Laurentians south of Wahnapitae. On the whole, 

 however, I should say that the Huronian series, in the broad belt 

 which runs far inland from North Channel, Lake Huron, contains 

 rocks of more than one age, some of which may prove to be more 

 closely connected with the Laurentian series ; but others are di- 

 stinctly later in age, and in some cases, perhaps, like our English 

 Pebidians, are not very much older than the Cambrian series. 



The specimens from the Huronian of Newfoundland are quite of 

 the last-named type. One, which I have examined, is a green flinty 

 slate, which might have come from Charnwoood Forest ; another is 

 an agglomerate, which, both macroscopically and microscopically, 

 bears a very close resemblance to specimens which I have described 

 from Tairffynnon and other localities near Bangor. 



Within the last few weeks, through the kindness of Prof. Boyd 

 Dawkins, I have had the opportunity of examining a small collection 

 of rocks and ^slides, illustrating the junction of the Laurentian and 

 Huronian, from the Lake of the Woods, Manitoba. I should not 



* Small crystals, apparently endogenous, of a brown mica are abundant. 

 The microscopic structure of the rock presents a resemblance to that of the Ober- 

 Mittweide conglomerate, described by Dr. Lehmann. For the opportunity of 

 examining the latter I am indebted to Mr. J. J. H. Teall. 



t To this belt of Huronians (in which, as said above, some Laurentians and 

 igneous masses are included) a breadth of about 100 miles is assigned. 



