FORMATIONS OF QUEBEC AND EASTERN ONTARIO. 23 



some places it is almost wanting, which makes it when pulverized a good material for glass. 



" The grains and particles in its composition are generally angular, but where it takes the 

 character of a conglomerate as it does in the inferior layers, they are frequently rounded. 

 The thicker strata exhibit an obscurely striped appearance owing to the prevalence of certain 

 colours in the different layers." ' 



The above description applies exactly to the rocks of the formation as developed in 

 western Quebec and eastern Ontario in the vicinity of the St. Lawrence and Ottawa rivers. 

 These rocks have been described in the Geology of Canada, 1863, by Sir William Logan, 

 under the heading of the Potsdam group, and their distribution is delineated with great 

 exactness. Owing, however, to the confusion prevailing at this date in regard to the other 

 members of the lower sedimentary and fossiliferous series, variously described under the 

 head of Taconic, the term Potsdam was by Billings made to include not only the typical 

 Potsdam, but certain of the other divisions as the Georgia slates and red sandrock of Ver- 

 mont, in which in 1861, Billings found trilobites of Primordial types, near the boundary 

 between Quebec and Vermont. It may however be mentioned that prior to this date no 

 detailed attempt had been made by the Canadian palaeontologist to study the Primordial 

 fauna as a distinct group of organic remains, and it was not till a somewhat later date that 

 Hartt in examining the fossils collected at St. John, N.B., discovered the existence of 

 Primordial t^-pes in that province. 



The typical Potsdam sandstone is somewhat local in its development. Tluis in northern 

 New York its distribution, as given by Emmons, shows it to be principally confined to the 

 counties lying more immediately south of the St. Lawrence and contiguous to Canadian 

 territory. In its extension into Canada it is well developed in the county of Huntingdon 

 which extends along the New York boundary from the St. Lawrence river to Missisquoi 

 bay at the lower end of Lake Champlain. Throughout this area the typical characters of a 

 grayish or yellowish-gray quartzose sandstone are preserved, and the strata are in a nearly 

 horizontal attitude or affected only by low anticlinals. East of Missisquoi bay this typical 

 character does not appear anywhere in Canada, though along the eastern shore, south of 

 Philipsburg, certain calcareous sandy beds probably represent the transition members between 

 the Potsdam proper and the Calciferous formation. This area has been carefully studied both 

 b}^ the Canadian and LTnited States palaeontologists and geologists and will be referred to again. 



To the west, the typical sandstone, as described in the Geology of Canada, 1863, crosses 

 the St. Lawrence from New York state to the vicinity of Brockville.' From this point it 

 follows westward along the outcrop of the Laurentian area, appearing at intervals from 

 beneath the overlying Calciferous beds to the vicinity of the Ottawa river, about twenty 

 miles west of the city of Ottawa, where it appears in the townships of Torbolton, Nepean 

 and Gloucester. 



Throughout the whole extent of its outcrop the Potsdam and the Calciferous preserve 

 for the most part a nearly horizontal attitude. At the crossing of the Ottawa river near the 

 Chat's rapids, the Potsdam sandstone is concealed by the overlying Calciferous beds or by 

 the heavy mantle of drift which has a wide distribution throughout the Ottawa valley. To the 

 eastward, outcrops of the typical sandstone are rarely seen till we pass the mouth of the 

 Gatineau river. Here at the mouth of a small creek which flows into the Ottawa river 



1 Geo. N. Y., vol. I., p. 215, 1837. 

 " Geology of Canada, 1863, p. 91 , 



