178 The Ottawa Naturalist. [January 



The geological structure of this area is confined almost 

 entirely to the Cambro-Silurian formations. To the north of 

 Hull, the old rocks of the Archaean approach within a short dis- 

 tance of that city, while to the west of Ottawa, in the eastern 

 portion of the township of March and in that part of Nepean ad- 

 joining on the east, similar granites, gneisses and limestones are 

 well displayed in a somewhat prominent ridge which extends 

 eastward from Arnprior. Resting upon these are the nearly 

 horizontal strata of the Potsdam sandstone and the Calciferous 

 limestone in their regular order, and in places these graduate 

 upward regularly into the Chazy and the succeeding formations, 

 to the top of the Cambro-Silurian series, which is capped by the 

 soft red shales of the Medina, in the adjacent township of 

 Russell. 



Much of the rock structure of Ottawa city is concealed at 

 the present time, and only occasional outcrops are visible at 

 widely separated intervals. Much information concerning these 

 hidden portions has been obtained, principally by Dr. Ami, from 

 an examination of the excavations made for drainage and for 

 buildings, and in this way we have been enabled to obtain a 

 fairly comprehensive idea of the geological structure of the 

 whole city. 



The oldest of the Palaeozoic formations, near Ottawa, are 

 the Potsdam sandstone and the Calciferous limestone, there 

 being no break between these two series of strata. These can 

 be well observed in the vicinity of Templeton station on the 

 Canadian Pacific railway, where the Potsdam sandstone rests 

 directly upon the Archaean gneiss and limestone and forms an 

 escarpment about thirty feet in height. These sandstones shade 

 upward into the Calciferous strata, which are well exposed in 

 the village of Templeton and along the road to the crossing of 

 the Wabassee Creek. These are the only Palaeozoic formations 

 seen in this part of the section. To the west of the city, in the 



