20 The Ottawa Naturalist. [April 



It is interesting- to note that, as one ascends the Ottawa, the 

 lower beds of the Palaeozoic series fail to appear. Thus, in the 

 lower portion of the river and as far west as the foot of the Chats 

 Falls about thirty-five miles west of Ottawa, the lowest formation of 

 the series, viz., the Potsdam sandstone, rests directly upon the 

 Archaean rocks. This is succeeded upward by the higher members 

 of the series. But even in early times there must have been heavy 

 breaks and uplifts, since, on the crest of the ridge of crystalline 

 rocks which extends eastward from Arnprior to within a few miles 

 of Ottawa on the south side of the river, a deposit of the Potsdam 

 sandstone is seen several hundreds of feet above the beds noted 

 near the river bank at Quyon, while a couple of miles further 

 south, this part of the series has been thrown down again by a 

 heavy break, to about the same distance. 



West of Arnprior the lowest beds seen along the river are of 

 Calciferous age, and these are last observed at the west end of 

 Allumette Island, above which no outcrops ot this formation have 

 yet been recognized. 



Further up the river, above the Roche Capitaine, which is 

 thirty-six miles below the Mattawa, the lowest beds are of the 

 Chazy formation, while on several of the islands in Lake Nipissing 

 beds of Black River age are found. On some ot the islands in < 

 the northern part of Lake Temiscaming fossiliferous limestones of 

 upper Silurian age occur which are about the horizon of the 

 Niagara formation The Black River beds of Lake Nipissing are 

 at nearly one hundred feet greater elevation than the Niagara beds 

 just mentioned, and about loo feet lower than similar limestones 

 seen in the vicinity of Clear Lake to the south of the Bonnechere. 



In all descriptions of the country toward the height of land, 

 north of the Ottawa, the occurrence of great areas of sand has 

 been pointed out. The origin of this sand deposit has never been 

 satisfactorily explained. The material appears to be largely the 

 result of the decomposition, or breaking down to a fine slate, of 

 the underlying- granite and gneiss which are the predominating- 

 rocks of the area. From the generally level character of the 

 country along this height of land isolated peaks rise to consider- 

 able elevations, though over long distances these are rarely more 

 than low hill features, scarcely exceeding a hundred feet in height, 

 above the general plain, 



