220 The Ottawa Naturalist. [March 



the concave side, facing the north, and is highest midway taper- 

 ing and spreading out towards both ends. Further observation 

 has shown that these ridges with sHght breaks extend eastward 

 through the city of Hull toward Lake Flora. Northward as far 

 as the Gatineau River there are many low ridges of rounded 

 boulders of much the same material as in the most northerly 

 ridge referred to above. 



The diversity both in the character and condition of 

 the material composing the first ridges described, taken in con- 

 nection with their proximity, makes it somewhat difficult 

 to account for their origin, Those lying to the north and ex- 

 tending to the Gatineau River are probably moraines, and were 

 left in their present position by ice moving down the Gatineau 

 Valley. 



The angular condition of the blocks in the most southerly 

 ridge shows that they have not been transported any very great 

 distance. The following section is from this ridge near 

 Chaudiere street and is in descending order, 



1. Large angular blocks of limestone mixed with sand and 



gravel, and an occasional rounded boulder of granite, 



etc 8 feet 



2. Fine sand and gravel 2 " 



3. Fine tough bluish stratified clay (Leda clay).' i^ " , 



4. Boulder clay 3 " 



5. Limestone rock in place, glaciated, striae, course S. 60° E. 



If No. I of this section is of morainic origin, then after 

 the ice which glaciated the underlying rock had receded, leaving 

 the boulder-clay, the land remained submerged long enough to 

 admit of the deposition of the clay and sand. (Nos 3 and 2 of 

 the above section) after which the ice again advanced, and 

 without displacing the underlying material deposited the lime- 

 stone blocks composing the ridge. Another explanation is that 

 it was formed by ice jams in the Ottawa River when it flowed 

 through the channel where Brewery Creek now runs. 



