igoi] Ells — Ancient Channels. 27 



Between the Carp and the present channel of the river, a well 

 defined ridge of crystalline rocks extends eastward from the 

 vicinity of Fitzroy to within nine miles of Ottawa city, where it 

 sinks down nearly to the level of the river and becomes covered 

 over with Potsdam sandstone. The south side of the ridge is 

 marked by a well defined line of fault which brings the Black River 

 limestones against the crystalline rocks. It is supposable there- 

 fore that an old channel of the river flowed eastward along the 

 depression in which the Carp River now lies. 



To the north of the crystalline rock ridge just mentioned a 

 second line of depression occurs also south of the Ottawa and 

 separated from it by another rock ridge formed of Chazy shale 

 and limestone. In this depression lies Lake Constant, and 

 Constant Creek flows thence westward to the Ottawa into a deep 

 depression known as Sand Bay. The elevation of the Creek and 

 Lake is but a few feet above the present level of the river, the 

 waters being sluggish throughout, and the depression extends 

 eastward through a swampy tract into the Ottawa again at Shirley 

 Bay a few miles West of Britannia. Great areas of reddish sand 

 occupy the shores of the Ottawa about the mouth of Constant 

 Creek and for several miles to the east and west. 



The north side of the Ottawa between Hull and a point some 

 miles west of the Chats Falls, practically as far west as the Ottawa 

 opposite the east end of Calumet Island near Campbell's Bay above 

 Bryson, is generally low and largely occupied by great deposits of 

 clay or sand. Occasionally well defined beaches are seen, as in the 

 area to the north-west of Quyon near the village of North Onslow, 

 where they are crossed by the road between these two places. 

 Occasional ridges of rock occur, as in the rear of the town of 

 Aylmer and north of Bristol station, but the main shore of the 

 river was at one time undoubtedly marked out by the great ridge 

 largely composed of reddish grey granite which rises in Kings 

 Mountain, west of Chelsea, and extends westerly for many miles 

 forming the northern limit of the great Ottawa plain. 



The lower part of the Ottawa must have been at one time 

 much broader and more delta shaped than at present. On the 

 north side the range of the crystalline rocks must have de- 

 fined the river much as at present, as far as the mouthy of the 



