518 REPORT OF NATIONAL MUSEUM, 1904. 



to above was made to include the Chazy and Calciferous formations 

 below the Trenton. 



It is worth} T of note that, while Logan's successors have been inva- 

 riably opposed to the idea of the origin of the drift and rock striations 

 through a glacial ice sheet, Logan evidently committed himself to 

 this theory. Concerning the origin of the lake basins of western 

 Canada he writes: 



These great lake basins are depressions, not of geological structure, but of denuda- 

 tion, and the grooves on the surface rocks, which descend under their waters, appear 

 to point to glacial action as one of the great causes which have produced these 

 depressions. 



Again, in a footnote on the same page, he quoted, with evident 

 approval, the following: 



This hypothesis (i. e., the origin of the lake basins) points to a glacial period when 

 the whole region was elevated far above its present level, and when the Laurentides, 

 the Adirondacks, and the Green Mountains were lofty Alpine ranges, covered with 

 perpetual snow from which great frozen rivers or glaciers extended over the plains 

 below, producing by their movements the glacial drift and scooping out the river 

 valleys and the basins of the lakes. 



It was in this same report that Logan first noted the occurrence of 

 a supposed fossil in the Laurentian of Canada, describing under the 

 name of Stromatqpora rugosa an aggregate of crystalline pyroxene 

 and calcite found by Mr. John Mullen in one of the bands of lime- 

 stone at the Grand Calumet. This was the so-called Eozoon of Daw- 

 son, referred to elsewhere. 



Logan, for his time, possessed a very profound insight into petro- 

 graphical problems, though he naturally regarded as traces of an 

 original bedding what is now known to be, in part, at least, foliation 

 due to djmamic causes. Thus, in his reports for 1853-1856, he wrote 

 concerning the rocks of the Laurentian system : 



They are the most ancient yet known on the continent of America, and are sup- 

 posed to be equivalent to the iron-bearing series of Scandinavia. Stretching on the 

 north side of the St. Lawrence from Labrador to Lake Superior, they occupy by far 

 the larger share of Canada, and they have been described in former reports as sedi- 

 mentary deposits in an altered condition, consisting of gneiss interstratified with 

 important bands of crystalline limestone (p. 7). 



And again: 



The Laurentian series are altered sedimentary rocks. 



The geology of the islands of Anticosti, Mingan, and the Magdalen 

 River region was assigned by Logan to James Richardson, who made 

 his report in 1857. The fossils collected were worked up by Billings, 

 who considered the rocks of the Anticosti group to consist of beds 

 of passage from the Lower to the Upper Silurian and synchronous 

 with the Oneida conglomerate, the Medina sandstone, and the Clinton 



