332 THE JOURNAL OF GEOLOGY. 



(3) A third view which has been advanced is that the Fun- 

 damental Gneiss is nothing more than a great mass of eruptive 

 granite or granitic rock which has eaten upward, and in places pen- 

 etrated the Grenville series, or perhaps absorbed it, while the Gren- 

 ville series itself represents a series of highly altered sediments 

 of Laurentian, Huronian or subsequent age. The enormous extent 

 and world-wide distribution of the Fundamental Gneiss forming 

 as it does wherever the base of the geological column is exposed 

 to view, the foundation or floor on which all subsequent rocks 

 are seen to rest, is opposed to this view of its origin, as is also 

 its persistent gneissic or banded character, although, as above 

 mentioned, much eruptive material is undoubtedly to be found 

 in it. 



Which of these views is correct can be ascertained only as 

 very careful and detailed mapping, accompanied by accurate 

 petrographical study, is proceeded with. In the present state of 

 our knowledge additional argument and discussion will not help 

 us toward the goal, while hasty work and generalization serves 

 but to retard the progress of our knowledge. 



The Anorthosite Series. — Associated with both the series of 

 rocks just described there are, as has been mentioned, great 

 eruptive masses of granite, some of which have been folded in 

 with the gneisses, while others evidently erupted at a much later 

 date, show no trace of dynamic action. 



In addition to these, basic eruptive rocks belonging to the 

 gabbro family occur in certain districts, sometimes in the form of 

 comparatively insignificant masses, but elsewhere underlying 

 great tracts of country. One on the upper waters of the Sague- 

 nay has an area of no less than 5,800 square miles. These 

 usually consist of a variety of gabbro in which the magnesia -iron 

 constituents are present in very small amount, being in many 

 cases entirely wanting, so that the rock consists practically of 

 pure plagioclase feldspar. These rocks were called miorthosite s 

 by Hunt, in the early reports of the Canadian Geological Survey, 

 on account of the great preponderance in them of "Anorthose,' 

 a general name given many years ago by Delesse to the triclinic 



