rX THE NORTH WEST OF CANADA. 81 



its sycamores, poplars, and oaks, and its curious fruit-beds. 



Hardly less impressive than the flaming era of volcanoes and 



earthquakes ; of torn and quaking rocks, which gave birth to the 



Rocky Mountains, is the contemplation of the remains of the 



Glacial Epoch. A vast pall of ice covered the whole width of 



the Continent ; glaciers filled the mountain valleys to above the 



level of 5,000 feet. Great blocks of Laurentian and Huronian 



gneiss, utterly unknown as a formation in the N. West Territory, 



were conveyed a thousand miles and more across the plains to the 



very foot of the Rockies. Laurentian boulders are found on a 



high ridge, once itself a moraine, at an elevation of 5,280 feet 



within a few miles of the Paleozoic rocks of the mountains. The 



usual height at which these erratics are found varies between 



4,000 and 4,600 feet: some are of enormous size, measuring 



42x40x20 feet, and 40x30x22 feet. An enormous glacier, 



already spoken of, ploughed its way between Vancouver Island 



and the Mainland, and this was but one amongst thousands of 



others. Everywhere they have left their traces : in terraces, on 



the mountain sides, up to the height of 4,500 feet. ; in drift 



deposits, to the depth of 200 feet over the prairies ; and on the 



plains thickly strewn with Laurentian erratics. 



The first great glacial epoch passed away, to be succeeded by 

 another of less severity and duration, and with this we will end 

 this " strange, eventful history." 



Vancouver. 



The Chlorophyll Grains in Lemna. — Stahl {Bot. Zeii., 



1880) states that in Lem?ia trisulca^ the chlorophyll grains, which 



in ordinary diffused light are ranged upon the two walls of each 



cell lying parallel to the frond's surface, at night are driven to the 



side walls or lowest wall, leaving the superficial one bare. Mr. 



Spencer Le M. Moore (Journ. Bot., Dec, 1888), in his observations 



on the subject, differs somewhat from these conclusions. His results 



show that while many of the grains are driven by darkness from 



the superficial to the side walls, many of them still remain on the 



superficial wall. This subject of photolysis is a very interesting 



one, and observers having duck-weed convenient would find in it 



a profitable field of investigation. — Bot. Gazette. 



Journal of Microscopy and Natural Science. 



New Series. Vol. II. 1889. i 



