Apeil 16, 1897.] 



SCIENCE. 



623 



tween the Cambrian and the Chazy-Trehton 

 limestones of Farnham. On the east side the 

 Cambro-Silurian succession involves the refer- 

 ence to a lower horizon than has been commonly 

 accepted, of the micaceous limestones which pass 

 into the group termed the ' Calciferous mica 

 schist' in the Vermont and New Hampshire 

 reports. This reference is based upon dis- 

 coveries of graptolites about Lake Memphrem- 

 agog clearly of the age of the lower Trenton. 



In the St. Lawrence plain country there are 

 very few strata referred to the upper Silurian ; 

 but on the Memphremagog side well-defined 

 Niagara and Devonian fossils are abundant. 



This area has also afforded much material for 

 petrographical studies in the series of bosses 

 and eruptive masses of diorites, diabase, syen- 

 ites and late granites extending from Stanstead 

 across the whole sheet to the Laurentian 

 gneisses and anorthosites of the northwest cor- 

 ner back of Montreal, a part of the original 

 Laurentian area of Logan. The anorthosites 

 are now clearly understood to have had an 

 eruptive origin ; and hence the original concep- 

 tion of an upper Laurentian or Labrador sys- 

 tem of stratified rocks is abandoned. 



The Dominion of Canada now furnishes us 

 the most important field for the study of glacial 

 phenomena. By slow degrees the existence of 

 an outer margin and various terminal or reces- 

 sional moraines has been proved for the United 

 States ; and it remains needful to explore the 

 districts farther north up to the Arctic regions 

 in order to find additional moraines and the 

 starting points of the ice movements. Dr. G. 

 M. Dawson, the Director of the Survey, has 

 given names to two parts of what has been 

 called the continental ice mass. One is the 

 Laurentian and the other the Cordilleran glacial 

 sheet, each with an independent existence, but 

 sending out ice streams which have coalesced 

 in the great western plains. The Cordilleran 

 mass was somewhat the smaller of the two, 

 having at its maximum development a length 

 of 1,200 miles. The main gathering ground or 

 nevS of this ice sheet lay between Latitudes 55° 

 and 59° ; and the ice flowed northerly, into 

 Alaska 350 miles, westerly into the Pacific 

 Ocean, southerly as much as 600 miles, into the 

 edge of the United States, and southeasterly 



over peaks rising to altitudes of over 7,000 

 feet ; thus implying a thickness of over 6,000 

 feet above the principal depressions of the sur- 

 face. Dr. Dawson thinks there were two max- 

 imum periods of glaciations in the Cordilleras, 

 followed by subsidences, in the first case 500 

 and in the second to 2,500 feet below the level 

 of to-day. There are numerous terraces of 

 boulder clay and white silts corresponding to 

 these levels. Indeed, judging from the descrip- 

 tions and views of these high terraces, there is 

 nothing comparable with them anywhere else 

 upon the continent. 



From the report of Mr. Low it would appear 

 that the central part of the Labrador peninsula 

 was the gathering ground of the Laurentian 

 ice sheet, from which glaciers flowed ofl" in all 

 directions, notably to the west, east and south. 

 The striae indicating the westerly movement are 

 the least distinct. 



Mr. Robert Chalmers reported upon the sur- 

 face geology of the maritime provinces. He finds 

 evidence of ice movements northerly and east- 

 erly from the higher elevations in northern New 

 England and Quebec, as well as southerly in the 

 St. Johns valley. No ice reached the peninsula 

 of Nova Scotia from the mainland except to a 

 very slight degree ; and the glaciation effected 

 is explained by supposing radial movements 

 from the Cobequids and the watershed of the 

 main peninsula. The general conclusion drawn 

 is that there was no movement from the St. 

 Lawrence valley up and over the New England 

 highlands towards the sea. All the phenomena 

 are to be explained upon the theory of local 

 glaciers moving outwardly to all quarters of the 

 compass from the greater mountains. Instead 

 of our going to Canada for the source of the 

 New England glaciation, the Canadians now 

 come to the White and Green mountains in 

 search of the ice which brought debris into the 

 St. Lawrence valley. The writer would remark 

 that these conclusions are undoubtedly correct 

 for one of the later epochs of glaciation. The 

 glaciers of the Champlain age entering the St. 

 Lawrence valley, both from the Labrador penin- 

 sula and the New England summits, brought 

 icebergs which floated over Montreal and Que- 

 bec and induced the severe climate, lasting for 

 a long time, which was suitable for the habita- 



