302 R. BELL — GLACIAL PHENOMENA IN CANADA. 



laid down upon :i map, some degree of parallelism is shown within the various 

 groups, yel the general bearings of these are bo different thai it is difficult 

 to s«e how they could have all been produced contemporaneously or by a 

 confluent ice-sheet : and yet, excepting far to the north, they all seem to be 

 equally old, and to have the same relations to the till. If any great interval 

 of time had elapsed between the production of these various Bets of grooves 

 we Bhould see greater differences among them than we do. A satisfactory 

 solution 'it' the problem requires more study than it has yet received, hut it 

 seems possible that the different groups, nearly equally distant from the 

 margin of the glaciated area, may have been produced within a few thousand 

 years of eacli other, their varying directions being accounted for by changes 

 in the slope of the land and by the greater or less quantity of ice existing 

 at the time — the course of a deep and wide glacier influenced by the general 

 contour of the country being different from that of a narrower one guided 

 by the more local features. In this way nearly all the grooves which had 

 been produced in a given region might he obliterated and replaced by another 

 Bet within a comparatively short time, leaving only traces of the earlier ones 

 behind. It would not, therefore, he necessary to suppose two distinct glacial 

 periods to account for such facts. 



Such changes in the direction of transportation would also serve to explain 

 some of the facts in connection with the composition of the drift. In order 

 to trace the distribution of the latter we require to choose some rock of a 

 well-marked character, situated far enough north, whose position ami bound- 

 aries are known. The peculiar and beautiful conglomerate of white quartzite 

 matrix with red jasper pebbles which occurs, BO far as we are aware, only 

 at the east end of Lake Superior and in the adjacent country north of Lake 

 Huron affords one of the best examples of this sort. Fragments of this 

 rock are found to the eastward all along the northern shores of Lake Huron 



a- far as French river, although the direction of the striae in the interval ami 



all around the northern part of Georgian bay 18 "SOUthwest. Worn pieces of 

 the same rock have Keen met with in the counties of Bruce and Huron, ami 

 Bouthward through the state of Ohio ami into Kentucky. A large bowlder 

 of this conglomerate, found in the southern part of the lower peninsula of 

 Michigan, bas been placed in the grounds of the State University at Ann 

 Arbor. This wide lateral dispersion from a small center and partly aw 

 the direction of the existing striae implies a shifting of t he drift materials by 

 successive glaciers pursuing different coursi 



Lakt Agasriz. Lei us now turn our attention for a few moments to Lake 



\ .-i--i/. 'I'll-- writer, having explored pretty extensively in the country 



between the site of this former lake and Hudson's bay, which is the mosl 



interesting field of inquiry in connection with questions :i- to the possibility 



of the existence of such a lake, may he allowed to add some remarks to 



