Of jSIaimanse^ L. Superior. 5 



which will be noticed hereafter. The numerous alternations of thin 

 sheets of trap and tufa that appear in the low ground around 

 this bay, indicate a long continued series of submarine volcanic 

 overflows, while the rounded pebbles in the conglomerate point to 

 a rocky Laurentian shore at no great distance. Much remains to 

 be done in this region in separating those igneous beds which 

 have consisted of volcanic ash and scoriae, from those which are 

 properly trappean ; but this is rendered very difficult by the con- 

 solidation of the fragmentary beds by zcolitic matter, and by 4lie 

 resemblance which hardened volcauic mud and beds of vesicular 

 scoriae bear to true overflows of amygdaloidal trap, as well as by 

 the changes induced in true igneous rocks by the percolation of 

 water. 



At the head of the bay, the ground rises rapidly to a height of 

 300 feet, in a succession of steep ridges, representing the outcrops 

 of the beds which succeed each other in descending order. The 

 section from the X. TV. extremitv of the bav inland is as follows 

 the measurements being taken from a plan prepared by Mr. Coats- 

 worth of the Bruce Mines, for the Montreal Mining Company, 

 who are now carrying on works of exploration at this place. The 

 dips are to the westward, the general strike being N. 10'^ to 20 

 W., and the angle of dip varying from 25^ to 35°. The rocte 

 are, as usual with such materials, very unevenly bedded. (See 

 section.) 



1. Alternations of trap and tufa, with a bed of conglomerate, 

 which appears to run out a little to the westward of the line of 

 section, in which it does not appear. Large veins of calc spar, 

 quartz, and laumonite occur in the trap, and some of them con- 

 tain small quantities of native copper, native silver, and galena. 

 Native copper also occurs in the vesicles of one of the amvgda- 

 loids, and one thin bed has its vesicles filled wdth a steatitic mi- 

 neral. These rocks occupy a breadth of 500 yards. 



2. Argillo-arenaceous beds, in places baked into a compact 

 jaspery rock of a fawn colour, with red dendritic stains, in other 

 parts a mottled argillaceous sandstone, similar to that of Aase 

 aux Crepes. Breadth 220 vards. 



3. Crystalline and Amygdaloidal Trap, with a bed of conglo- 

 merate. These rocks occupy a breadth of 440 yards, and rise to 

 an elevation of 300 feet. The old Indian workings and the ex- 

 cavations of the present mine are on the summit of this ridge. 

 The lowest rocks of this band are probably tufacous, and have 

 been excavated into the ravine of a small brook. 



