234 Canadian Record of Science, 



Distribution of Potsdam Sandstone. 



The recent surveys made by the railway engineers be- 

 tween Eideau and Elgin emphasize the suggestion I have 

 elsewhere made that the Potsdam sandstone has probably 

 had a wider distribution throughout this Laurentian 

 isthmus than was at first supposed. After leaving Eideau 

 Station on the Grand Trunk Eailway, the sandstone is 

 met with on lot 9 in the 4th concession of Pittsburg 

 whence it continues to lot 11 in the 5th concession. The 

 beds furnish an excellent building stone. It appears again 

 in the middle of lot 12 in the 5th concession and continues 

 to lot 15 in the same concession when the gneiss again 

 takes its place. Further on, at Brewer's Mills, a few feet 

 of sandstone cap the low Laurentian ridge to the north of 

 the locks, and at the outlet of and at places around, Lough- 

 borough Lake a few miles farther north, and also around 

 Knowlton Lake, it is also found. Immediately beyond 

 Morton, on lots 4 and 5 in the 5th concessiou of South 

 Crosby, and at Jones Falls it reappears, at the latter place 

 forming cliffs of about 70 feet in height. The splendid 

 locks and dam at Jones Falls are built of sandstone. East 

 of Morton it probably underlies the broad stretch of flat 

 country lying between that village and Lyndhurst and 

 thence towards Seeley's Bay. Beyond Lyndhurst about 

 Bass Lake and on the north side of Charleston Lake, it is 

 also met with. On the north western side of Lower 

 Eideau Lake and continuing to Perth aud thence north to 

 about the Mississippi Eiver within a short distance of 

 Lanark, there is a broad display of the Potsdam sandstone 

 It appears also in South Elmsley, and at Portland in 

 Bastard has been used as a building material, though the 

 upper rocks in this vicinity may be of calciferous sand rock. 

 Among and in the neighborhood of the Thousand Islands, 

 the Potsdam sandstone occurs at one or two points on the 

 St. Lawrence side of the Township of Pittsburg, at and 

 around Gananoque, on the lower end of Howe Island, and 

 on Hay, Tidds, and parts of Eound and Wellesley Islands, 

 whilst farther down the river, it appears near Alexandria 



