[ells] the ARCH^AN of EASTERN CANADA 11» 



wick, and this feature was pointed out some years ago by Sir Wm. Dawson 

 and Dr. Honeyman. The latter, also, noted their similiarity to certain 

 rock masses found in Guysborough and Antigonish, which were also re- 

 garded by Honeyman as of Archœan age. This resemblance of the Cobe- 

 quid mountain cr3^stallinc rocks to the recognized Pre Cambrian of New 

 Brunswick, together with the schistose character of certain portions of 

 the series at several points, has led to their provisional classification in the 

 same series. The fact, however, that certain of the igneous masses pene- 

 trate the Devonian plant-bearing beds on the south side of the mountain, 

 in which are situated the iron ores of Londonderry, and other places to the 

 east and west, as well as the Silurian of Wentworth on the north side of 

 the range, clearly shows that a large part of these igneous rocks is 

 comparatively recent. These facts, together with the absence of all Pri- 

 mordial rocks in this area, or, in fact, of any strata, in so far as yet 

 observed, older than the Upper Silurian, may be taken as presumptive 

 evidence that the greater portion, at least, if not all, of the rocks of this 

 mountain chain Juay, with propriety, be regarded as more recent than 

 Pre Cambrian. Where the intrusions have penetrated the Devonian slates, 

 these are frequently converted into schistose strata, which present features 

 closely resembling the schists of the western areas. Similar instances of 

 the changing of Silurian and 1 'evonian slates into Huronian looking 

 schists occur in the Eastern Townships of Quebec, around the shores 

 of Memphremagog lake, where igneous rocks are also well seen in contact. 



It is possible that much of the rock of the Antigonish and Guys- 

 borough areas, also at one time regarded as of Pre-Cambrian age, will be 

 found to belong to a more recent date. The granites, felsites and green- 

 stones which there occur are similar to those seen in the Cobequids, and 

 there is also the same absence of Primordial strata, while the overlying 

 associated beds are of Silurian and Devonian age. 



The changes which have been made in the last twenty years in the 

 classification and determination of the various rocks which make up the 

 Archaean masses of Canada, and which were formerly assigned to the 

 Laurentian system, have been very marked. Among the most impor- 

 tant of these are the results of the examination of the igneous portion of 

 the older crystallines ; and a series of ob.servations, both in the field and 

 by the aid of the microscope, has shown conclusively that many of the 

 masses, once regarded as of sedimentary origin, are, in reality, altered 

 igneous rocks. Among the most important of these changes is the 

 placing of the great masses of the Anorthosite rocks north of the St. 

 Lawrence in this category, and their removal from the place they so long 

 held as an upper portion of the Laurentian sediments, it has now been 

 well ascertained that these have penetrated the crystalline limestone and 

 quartzites of the Laurentian, and are, consequently, of more recent date 

 than the Grenville division of that system. They frequently cut off 



