65 



The Ottawa Naturalist 



[Vol. XXXII. 



This slight sketch is submitted to the readers of 

 The Ottawa Naturalist as a study in geography. 

 We start with the hypotheses that every city, town 

 and village in the Ottawa valley began at a water- 

 fall, or on an old transportation route and gradually 

 developed according to certain influences which 

 may or may not be connected with geography. 

 PHYSICAL GEOGRAPHY AND GEOLOGY. 



Archean upland merges into the valley plain on a 

 gentle grade with no well marked escarpment. The 

 abrupt transition from the valley plain to the upland 

 IS probably seen to best advantage between Kings- 

 mere and Eardley beginning a few miles northwest 

 of the city of Ottawa. The valley wall is here 

 about 700 feet high and forms a marked contrast 

 to the Ontario boundary on the opposite side of the 



The Ottawa valley is a wide depression extending valley between Carleton Place and Perth where it 



in a northwesterly direction. It is bordered by a is merely a gently sloping ridge about 100 feet above 



generally well defined escarpment of Archean rocks the inner edge of the plain. 



mostly granite gneisses. The river flows down this The great upland of which these escarpments are 



depression through a series of long narrow quiet features is often referred to in various literature as 



MAP OF A PORTION OF THE OTTAWA VALLEY. 

 The heavy dotted lines indicate approximately the escarpments bounding 

 the valley plains. Nearly all the towns and villages and the bulk of the popula- 

 tion in the region shown by the map are included in the area between the 

 dotted lines. 



water reaches, called lakes, which are connected by 

 much narrower and shorter stretches of rapids or 

 falls. The river forms the boundary between the 

 provinces of Ontario and Quebec. 



The elevation of the river is 127 feet above sea 

 level at Ottawa and 364 feet at Pembroke, the dis- 

 tance between these points being about 90 miles. 



The escarpment on the Quebec side of the river 

 rises in places to a height of 1000 feet above the 

 river levels, and often presents a wall-like aspect, 

 but on the Ontario side it is not so abrupt, especially 

 in the southern portion of the valley, where the 



the Laurentian mountains or the Laurentian plateau. 

 Geologists often call it the Archean upland because 

 it is composed wholly of rocks which as far as they 

 know are the oldest in the world, and they usually 

 stand at a higher elevation that the Paleozoic rocks 

 which form a fringe around their southern and 

 northern edges. 



The Ottawa valley is more or less plain-like in 

 the southern part and has a width of about 28 miles 

 in an east-west direction between the escarpment 

 near Ottawa to that at Almonte. At Arnprior the 

 width of the valley is about 18 miles. Above this 



