132 THE CANADIAN NATURALIST. [Yol. X. 



ton aud Hudson River groups of America) of the New York 

 Geological Survey, under the name Cambro-Silurian — a name 

 given by one of the fathers of Pjnglish Geology (Professor Sedg- 

 wick) before Sir R. Murchison included their Welsh equiva- 

 lents as the lower portion of his ''Silurian System," as the 

 character of the organic remains is intermediate between Sedg- 

 wick^s Camhrian and Murchison' s Original Silurian Systems. 



In the State of New York the Niagara group is divided in 

 ascending order into the Oneida, Medina, Clinton and Nia- 

 gara EPOCHS, and overlies the Hudson River formation. 



The Oneida of New York consists of a conglomerate, and is 

 wanting in Canada, but all the other members of the series are 

 present in the Province. At the head of Lake Ontario, the 

 Medina is underlaid by the rocks of the Hudson River epoch ; 

 and the rocks of the Niagara period form the surface deposits 

 adjacent to the lake region, while twenty miles to the westward, 

 they are overlaid in the neighbourhood of the towns of Gait and 

 Guelph by the deposits of the Guelph formation. 



In the Niagara Peninsula, south of Hamilton, the Niagara 

 formation is succeeded by some of the members of the Helder- 

 berg group, unless there be some thin concealed deposits of the 

 Guelph group not exposed. 



The general dip of the whole series is 25.5 feet in the mile in 

 a direction of about twenty degrees west of south. 



III. — GEOLOGICAL SECTIONS. 



During the summer of 1879, the writer, with the assistance 

 of the late George Beasley, Esq., C. E., made instrumental 

 measurements of four Geological Sections — the most complete 

 that could be obtained. Two of these sections were at Dundas, 

 one at Hamilton, and one south-east of the city, from the water- 

 shed between Lake Ontario and Lake Erie, along the exposures 

 of the Niagara Limestones in the bed of the Rosseaux Creek, to 

 its falls at Mount Albion. These measurements required several 

 days' levelling over many miles of ground. In addition to the 

 principal sections, several smaller exposures were measured in 

 order to compare the continuity of various strata. 



The thickness and character of the lowest portions of the 

 Medina formation were ascertained from the log of an Artesian 

 well, sunk to a depth of 1600 feet, in the western part of Dundas. 



