280 ASSINNIBOINE AND SASKATCHEWAN EXPEDITION. 



true Lower Silurian fossils, we know that the former must 

 be of Cambrian age. We further learn that the old or 

 fundamental gneiss, which lies beneath such Cambrian 

 sandstone, and is entirely unconformable to, and indepen- 

 dent of it, is a lower stratified rock than any hitherto re- 

 cognized in the British Isles. The beginning of the geo- 

 logical alphabet, as applied in the Maps of the Geological 

 Survey to the Cambrian rocks of England, Wales, and 

 Ireland, must therefore be preceded in Scotland by the 

 first letter of some alphabet earlier than the Eoman, show- 

 ing a still lower deep in the north-west of Scotland (as 

 in North America) than exists in England, Wales, or 

 Ireland. 



" If this most ancient gneiss required a British name, it 

 might indeed with propriety be termed the 6 Lewisian 

 System,' seeing that the large island of the Lewis is es- 

 sentially composed of it, capped here and there by de- 

 rivative masses of Cambrian conglomerate ; but the term 

 ' Laurentian ' having been already applied to rocks of 

 this age in North America by our distinguished associate 

 Sir W. Logan, I adhere to that name, the more so as it is 

 derived from a very extensive region of a great British 

 colony." 



THE HUR0NIAN SERIES. 



The Huronian series has not been recognized in the 

 basin of Lake Winnipeg, but as it rests unconformably 

 on the Laurentian rocks for a distance of nearly 500 

 miles on the shores of Lakes Superior and Huron, occur- 

 ring both on the north and south shores of the first- 

 named lake, it is not improbable that it will be found to 

 exist in the Winnipeg Basin. In Canada it contains 

 very important metalliferous veins, particularly of native 



