RELATIVE DATES OP INTRUSIVE ROCKS. 109 



seen in the ice-grooves of the vicinity makes it probable the country 

 has been much worn down by denuding agencies. In this vicinity 

 some entangled beds of gneiss were met with, one of which was 

 traced for upwards of a hundred yards, running about "N 70° W. 

 It was surrounded by the porphyritic rock. 



Erom this porphyritic nucleus one or two porphyritic dykes were 

 traced, cutting the syenite for short distances, and some of a similar 

 character were met with at such a distance as to make it probable ' 

 that there are other porphyritic nuclei. 



In the vicinity of the pear-shaped porphyritic intrusion which was 

 first described, there are met with two veins of a special character, 

 cutting the syenite, that deserve to be noticed. They consist of 

 cellular chert, from white to yellowish-brown, or fiesh-red, the colors 

 in some cases running in bands parallel to one another, and some- 

 times rather confusedly mingled, giving the aspect of a breccia. The 

 cells are unequally distributed, some parts of the veins being nearly 

 destitute of them, while in other parts they are very abundant, and 

 of various sizes, from that of a pin's head to an inch in diameter. 

 On the walls of some of these cells or druses, small transparent 

 crystals of quartz are implanted, and in some there are the impres- 

 sions of cubical forms, resulting probably from crystals of fluor-spar 

 which have disappeared. On analysis, Mr. Hunt finds that the stone 

 yields eight per cent, of soluble silica, and approaches in its compo- 

 sition to the nature of flint. From its cellular structure it would 

 make a very good buhr stone. 



The chief vein is on the land of Sir. Lowe. It appears to run in 

 a very straight line, of which the bearing is about east and west, and 

 it stands in a vertical attitude, while its breadth varies from four ta 

 seven feet, being apparently, however, in one place, nearly tv/enty. 

 In the wider parts there are seen, in the middle of the vein, masses 

 six or eight inches thick, of the syenite, which constitutes the wall 

 rock. Where the rock is banded the colors run parallel with the 

 sides. The attitude and associations of the mass clearly show that 

 it cannot be of sedimentary origin, and the soluble silica which it 

 contains, with the volcanic character of the district, suggest the 

 probability of its derivation from hot springs similar to the Greysers 

 of Iceland. "Waters holding silica in solution have deposited this 

 material upon the walls of crevices in the syenite, ultimately filling 

 them up. 



The intrusive rocks which have been described have a date anterior 

 to the fossiliferous formations. None of a similar character have 



