REPORT OF TEE CEIEF ASTRONOMER XXI 



SESSIONAL PAPER No. 25a 



Page. 



Genetic classification of magmas 778 



Application of the theory to the Forty-ninth Parallel rocks 779 



Introduction , 779 



Evidence of a primary acid earth-shell 780 



Evidence of a basaltic substratum 780 



Syntectics 783 



The granites 784 



The granodiorites 784 



The diorites and acid andesites 785 



The complementary dikes and sheets, and the pegmatites 786 



The abnormal gabbros 787 



The alkaline rocks 788 



APPENDIX < A.' 



Table of chemical analyses 793 



APPENDIX 'B.' 



Eeport on fossil plants, by Professor D. P. Penhallow, D.Sc F.G.S.A.. . 800 



ILLTTSTKATIONS. 

 PLATES, 



1. Frontispiece. — Terminal Boundary monument set by the first International 



Commission at the Pacific shore. 



2. Profile sections showing relative reliefs of the Alpine chain, the Himalayan 



chain, and the part of the Cordillera of North America between the Gulf 

 of Georgia and the Great Plains. 



3. Map illustrating proposed subdivision of the Cordillera in the vicinity of 



the Eorty-ninth Parallel. 



4. Boundary slash across the Rocky Mountain Trench at Gateway. 



5. Looking east across the Purcell Trench, from western edge of Kootenay 



river delta near Corn creek. 



6. Belt of the Interior Plateaus; looking north from near Park mountain, 



Okanagan range, over Ashnola river valley. 



7. Looking down Kintla Lakes valley. 



8. Cameron Falls on Oil Creek at low-water season. 



9. Mount Thompson, seen across Upper Kintla Lake. 

 10. A. — Sheared phase of Siyeh limestone, Clarke range. 



B. — Sheared phase of dolomitic lense (weathered) in Kitchener formation, 

 at Tahk river. 



