[6441 



NOTE ON THE OCCURRENCE, NEAR TORONTO, 



OF BOULDERS BELONGING TO THE CALCIFEROUS 

 FORMATION. 



BY GEORGE JENNINGS HINDB, F.G.S. 



(Read he/ore the Canadian Institute, December ISfh, 18H7.) 



Amongst the numerous erratic boulders scattered on tlie surface of 

 the country to the north and west of Toronto, there are, not un- 

 frequently, some of a very hard bluish-gray rock, composed of 

 rounded grains of quartz-sand imbedded in a calcareous cement. 

 Through weathering, the calcareous portion of the exterior of these 

 boulders is dissolved away, leaving a crust, of an inch or so in thick- 

 ness, of a reddish-brown friable sandstone. As a rule, the boulders 

 are rounded in figure and from eight inches to two feet in diameter, 

 No traces of glacial strise are present, and even had such been formed, 

 they would most probably have been obliterated through the decay 

 of the outer surface. The majority of these boulders are destitute of 

 organic remains, but I have lately found some filled with the casts 

 of Ophileta compacta : Salter. This shell is characteristic of the Calci- 

 ferous formation, and as the material of the boulders is also identical 

 in character with the rocks of that formation, and very distinct from 

 any other known rock in this portion of Canada, it may be concluded 

 that the non-fossiliferous, as well as the fossiliferous, boulders have 

 been derived from the same source. The calciferous formation pre- 

 vails in a very extensive area between the St. Lawrence and Ottawa 

 Rivers in the eastern portion of this Province of Ontario, but it is 

 not known with certainty to occur on the western side of the Lauren- 

 tian spur crossing the St. Lawrence at the Thousand Isles. Thus 

 the nearest localities from which the boulders in question could have 

 been derived are about 200 miles distant, in a direction between the 

 angles of IST. 55 E. and N. 71 E. from Toronto. The boulders are 

 found at levels of 350 to 450 feet above the sea, which is, if any. 

 thing, slightly higher than the present general level of the rock-beds 

 from which they have been brought. 



