THE ANALYSES. 



15 



TABLE 8 Continued. 



1 Carbonated. 



2 No. 17. Analysis (by Strong): Si0 2 , 49.15; A1 2 O 3 , 21.90; FCjA, 6.60; FeO,4.54; CaO, 8.22; MgO, 3.03; NaO,3.83; 

 KoO, 1.61 ; HoO, 1.92 ; 100.80. 



s No. 19. Analysis ( Riggs, Bull. 62, p. 113) : SiO, 54.83 ; A1 2 3 , 25.49 ; Fe 2 3 , 1.61 ; FeO, 1.65 ; CaO, 6.08 ; MgO, 1.96 ; 

 NaoO, 5.69 ; K.,O, 1.87 ; H 2 O, 1.18 ; CO 2 , .18 ; 100.54. 



4 Nos. 19, 20, and 21 were collected from an intrusion of granite-gneiss into greenstone, which has been called 

 Upper Huronian by Brooks, the granite-gneiss being placed at the top of the Upper Huronian. Bulletin 62, p. 26. 

 This series shows a gradation from massive porphyritic granite to very fine-banded gneiss. No. 19 is from the center 

 of the intrusive dike, and grades almost imperceptibly on both sides into the fine-grained gneiss of which No. 20 is the 

 type. No. 21 is similar to No. 20, being on the sides, but is banded. This rock is more basic than typical granite, 

 being more like a diorite in composition. The low gas-volume of No. 20 in comparison with the two other speci- 

 mens is perhaps to be explained by the fact that it is a much more porous rock, crumbling readily to a fine powder 

 on the anvil. 



5 Owing to an accident during the explosion it was impossible to determine the relative amounts of CH 4 , H 2 , and 

 No, but the violence of the explosion suggests that there was little N 2 present. 



