22 ROYAL SOCIKTY OF CANADA 



From the fact that so hirge an extent of tlie Dominion of Canada 

 is occupied by tlie oldest crystalline gneiss and granite with intimately 

 associated limestone and quartzite, their study in tlie field has, from a 

 Tery early date, presented specially attractive features. In the earliest 

 publications of the Geological Survey, frequent references are made to 

 these old rocks, and so important did the question become, in view of 

 the complicated problems involved in their study, that, in 1853, Logan 

 began a detailed examination of an area along the lower Ottawa, in which 

 the township of Grenville is located, where it was hoped a typical field 

 for the investigation of the princi^jal dillicullies encountered might be 

 found. The study of this area in Grenville, and that of the country to 

 the north along the Eiver Kouge, and east in the direction of Morin and 

 St. Jerome, occupied several seasons and resulted in the formation of a 

 scheme of classification for these rocks which, for many years, has been 

 held as the standard by which the whole Laurentian complex has been 

 largely determined. This group of rocks comprising certain gneisses, 

 limestones and quartzites soon became known as the Grenville series, the 

 first descriptions of which appeared in the Eeport for the year 1857, 

 which were further elaborated in the Geology of Canada, 18G3. At this 

 time the Laurentian was held to consist of three divisions, viz., that just 

 described, which was held to rest upon an older series of gneiss and 

 granite, which was styled the Fundamental or Ottawa Gneiss, and an 

 upper member, consisting principally of anorthosite or labradorite 

 rocks, which, from a gneissic structure existing in portions of the mass, 

 and from a supposed overlapping of these upon the crystalline limestones 

 of the Grenville series, was held to represent an altered group of sedi- 

 mentary strata, and to form a unconformably upper member of the 

 Laurentian. 



About the same date on which Logan began his study of the Gren- 

 ville rocks the examination of a very similar group was undertaken by 

 Murray in the region north of Kingston, more particularly in the county 

 of Hastings. This work, begun by Murray in 1853, was resumed by 

 Macfarlane in 1865, in connection with the occurrence of minerals of 

 economic importance, which were found in that district, and to this work 

 Vennor succeeded in the following year. In his report on the rocks of 

 this area, Macfarlanu pointed out the resemblance of certain portions, 

 of what were then denominated the Hastings rocks, to the recognized 

 Huronian of other localities, as evidenced more especially by the occur- 

 rence of certain conglomerates. To this view, however, Logan took ex- 

 ception, and would not admit their Huronian age, but supposed that they 

 might represent a higher portion of the Lower Laurentian series than 

 had been met with elsewhere. In a foot note in which Logan expresses 



