260 Geology and Mineralogy of the 



but running both abruptly and insensibly into cream or 

 straw yellow, red, blue, and light green. It clearly observes 

 a north west course, either at a high angle north east, or ver- 

 tically. This greenstone is a slate on the south east side of 

 the excellent harbor at the west end of the promontory. 



The greenstone of the contiguous large island (proceeding 

 north west) is at first for a short distance brown, in shades, 

 and slaty, and then becomes almost pure hornblende, split- 

 ting into thick blocks, and containing few or no nodules ; 

 occasionally however changing to a reddish hue from a pre- 

 dominance of feldspar, as the flattened rhombs of that min- 

 eral in the fissures would seem to indicate. The rock soon 

 after continues to the end of the island in the form it wore 

 on the promontory, with smaller granitoid nodules. Some- 

 times the splinteriness is remarkably great. The direction, 

 &c. continue the same. 



At the spot where the hornblende is most abundant, thin 

 waving veins of ligneous asbestus traverse the rock for some 

 yards. The matrix is so difficultly frangible that I could 

 not remove specimens more than two inches long. It shews 

 itself by insensible gradations ; the centre only of the vein 

 being perfect. Here are also vertical veins of quartz half a 

 foot in diameter, containing cavities lined with hexahedral 

 prisms of great size. The surface of the rock occasionally 

 takes a polish and becomes undulatory. In the concave 

 portion there is often a round congeries of small and very 

 brilliant rock crystals of a honey yellow color, which at- 

 tracts the eye immediately. The only other foreign mine- 

 rals I found are galena, in a thready vein three yards long, 

 dipping obliquely into the rock, and calc spar. 



The bluff at the lower end of the narrows (which are two 

 and a half miles long) is also greenstone passing into the 

 slaty species, and is here penetrated by a strong seam of 

 quartz, containing much of what I conceive to be copper 

 pyrites in mass, and in obscure octohedral crystals. The 

 sound part yields readily to the knife, and is every where 

 encircled with yellow and green crusts of various shades. I 

 am at present unable to apply the proper tests from not hav- 

 ing access to the specimens. 



On passing upwards along the line of precipices constitu- 

 ting the narrows of the north channel to St. Mary's, we find 

 the rock to take a reddish brown hue, and to become very 



