40 PEOF. T. G. BOI^NEY OX THE HT7EOXIA2f SEEIES 



distance, all 1| mile from Sudbury ; these, in the field, especially 

 when weathered, as Dr. Selwyn pointed out, have a marked resem- 

 blance to beds of volcanic ash. The matrix has a general similarity 

 to that of the schistose rock described above, except that the mica 

 flakes (brownish or greenish, possibly in some cases a chlorite, and 

 ■white in variable proportions) are rather larger, and the rock, as a 

 whole, is nearer to a typical mica-schist. The fragments have a 

 general structure resembling that described above, but the mosaic 

 structure is less strongly defined, and there is, in one case, much 

 more mica, especially white. They are not porphyritic, as in the 

 other instances. 



I travelled over the great belt of the Huronian, mapped as ex- 

 tending for more than 70 miles from Sudbury *, as far as Pagama- 

 seng (59 miles), where the track ended at the time of my visit, but 

 could only examine the rocks here and there, and then hastily. 

 Still as the train went very slowly, and I was in an open van, I could 

 form some notion of their general character. I believe that Lauren- 

 tian gneiss is brought up by faults two or three times, the inter- 

 vening and dominating rock being Huronian, interrupted occasionally 

 by intrusive masses of granite, syenite, or diorite. It is, however, 

 hardly worth while my transcribing notes gathered on a hasty 

 traverse. I will merely say that near the east end of Geneva lake is 

 a grand conglomerate which contains blocks of a grey granite-like 

 rock, passing westward into a dark-grained slaty rock, interstratified 

 with a grey quartzite distinctly banded with quartz-pebbles. Near 

 Vermillion Eiver I obtained an ordinary grey wacke. At High Falls, 

 on the Oneping (25 miles from Sudbury), we cut through a mass of 

 fragmental rock like a volcanic ash, which is worth notice. The 

 finer matrix is almost opaque, a very dark dust ; the smaller frag- 

 ments are quartz (not abundant) and altered felspar or devitrified 

 glass. The larger have probably been a moderately acid glass, some- 

 times vesicular, the cavities being now occupied by a pale chloritie 

 mineral, the matrix beiog partly microcrystalline, partly a mass of 

 small felspar crystallites, with occasional groups of pale actinolite. 

 The zonal arrangement of some of the evitrification-structures sug- 

 gests that the changes have taken place in situf. 



The remaining specimens in my collection, not from the above 

 line of section, and almost all given to me by Dr. Selwyn as typical 

 varieties of the Huronian group, may be classified as follows : — 



(1) Eocks little altered. These are grits, the fragments evidently 

 being waterworn. One (from an island on Lake Huron between Del- 

 ormine and Boulanger locations) contains in a rather earthy matrix 

 fragments of three distinct varieties of lava : one is a very character- 



* Measured on the map, Sudbuiy is about 12 miles by the railway from 

 the eastern boundary of the Huronian. but the railway is here running about 

 W.S.W. The total breadth of the Huronian belt, as mapped, is probably nearly 

 80 miles, measuring in a N.W. direction, the preralent dip iDeing roughly S.E. 



t I obtained a specimen thus: the guard kindly jumped off the train as it 

 was going along, and picked up a block for me ! I mention this to show that 

 the pace of a "construction " train on a new line gives more opportunity for 

 geological obserration than do modern expresses. 



