1869.] WALLBRIDGE CANADA WEST. 271 



many of whicli possess considerable value in an economic point of 

 view. The most important of these is Galena, extensive deposits of 

 which may be traced for a considerable distance through the town- 

 ships of Tudor and Lake. It is notable that the lead-ores thus 

 enjoy a geographical distribution entirely distinct from that of the 

 iron-ores. The Galena usually occurs in a gangue of calcareous spar, 

 and forms veins or lodes coursing through the Laurentian Lime- 

 stone or calcareous schists. Copper-ores have been found, as pre- 

 viously stated, but never in sufficient quantity to render their 

 working remunerative. A small and unimportant deposit of anti- 

 rnonite, or sulphide of antimony, has been found in the township of 

 Sheffield. Plumbago, of greater or less purity, is occasionally met 

 with in the Laurentian limestones of the county, but has not 

 hitherto been worked. 



Pinally, attention may be directed to two other minerals, which, 

 although of no economic value, are of mineralogical interest as 

 species that have not hitherto been described from this county. 

 One of these is Butile, or oxide of titanium, which I have found 

 penetrating the quartz of Hog Lake in the form of stout prismatic 

 crystals, striated longitudinally, and presenting a hair- brown colour 

 and a strong lustre. The other mineral is Schorl, or black tourma- 

 line, which occurs on lot fifteen of range four in Madoc, as a reticu- 

 lated mass of slender prismatic crystals imbedded in quartz. 



Discussion. 



Prof. Ramsay inquired as to the proof of the existence of so large 

 a boulder as one of five acres in extent. Under ordinary circum- 

 stances large boulders fell from higher rocks on to the surface of 

 glaciers beneath, and were by them transported to the places where 

 now found ; but the fall of such a mass seemed almost incredible. 

 He suggested that possibly it might be a boss of the Lower Lauren- 

 tian beds standing out through Silurian strata. 



Mr. David Eorbes stated that the results of his own examination 

 of some of the specimens from the gold-mines of this district did not 

 quite tally with those recorded in the paper, especially those of the 

 rocks in the neighbourhood of the veins. He considered that the 

 gold in Canada was confined to the veins. 



Mr. Prestwich cited the discovery of a boulder between Grantham 

 and Peterborough, which was at least 400 feet in length, and con- 

 sisted of a mass of Great Oolite. 



Mr. Seaeles Wood mentioned a boulder of marl in the coast- 

 section near Cromer upwards of 300 yards in length, and 60 feet in 

 height. 



Mr. Wallbridge, in reply, stated that the rock must have come at 

 the least twenty miles from its original home. The surface of the 

 Trenton limestone rock in the neighbourhood was striated in the 

 direction of the boulder. There was no evidence of intrusion. The 

 mass was traversed in two or three places by crevices. 



