478 



Canadian Record of Science. 



I may add here that Dr. F. I). Adams has found that 

 in certain localities the rocks of the Grenville Series be- 

 come almost horizontal, though even in this case they 

 show evidence of having been subjected to much alteration 

 and great pressure. He has also shown, by comparison of 

 a number of detailed analyses, that several of the gneisses 

 of the Grenville Series have the chemical composition of 

 Palaeozoic slates, snd thus that there can be no chemical 

 objection to regarding them as altered sediments. This I 

 consider a very important observation ; and I may refer 

 for details to his paper in the American Journal of Science, 

 1895, p. 58. 



The summary of facts above given should, I think, be 

 sufficient to show that in the case of the Grenville lime- 

 stone we have phenomena which cannot be explained by 

 mere pressure acting on massive rocks, or by segregation 

 of calcite from igneous rocks, or by vein structures, or by 

 any contact structures arising at the junction of igneous 

 and aqueous deposits. We have, on the contrary, to deal 

 with a formation which indicates that in the early period 

 to which it belongs regular sedimentation was already in 

 full operation. The more precise vital and chemical 

 agencies which prevailed in the ocean of the Laurentian 

 period we must notice later. 



I have merely to add here that the characters assigned 

 above to the Grenville Series have not only been fully 

 corroborated by the recent work of Adams and Ells in 

 Canada, 1 but also by the surveys of Kemp and Smyth in 

 the more disturbed and elevated district of the Adirondack 

 Mountains in New York. 2 



We have thus paved the way for the consideration of 

 evidence of a structural and chemical character. 



To be Continued. 



i American Journal of Geology, 1893, No. 4.^ Also Reports Geol. Sarv. of Canada. 

 2 Bulletin Geol. Soc. of America, March, 1895. 



