132 
The city of Hull is built partly on a ridge of Trenton 
limestone and partly on a series of wide flal-topped boulder 
ridges somewhat resembling small terminal moraines. 
A section of one of these ridges near a quarry in 
Trenton limestone shows 10 to 20 feet (3-0 to 6-1 m.) 
in thickness of large angular blocks of limestone, occa- 
sional well rounded boulders of Pre-Cambrian rocks, 
and a small quantity of waterworn gravels and stones. 
The limestone slabs lie mostly in an imbricated manner, as 
if they had been acted upon by some powerful thrust. 
The following section is from the most southerly ridge 
near Chaudiére street and is in descending order :— 
1. Large angular blocks of limestone mixed with sand, 
gravel, and an occasional rounded boulder of granite, 
etc., 8 feet (2-4 m.). 
2. Fine sand and gravel, 2 feet (-6 m.). 
3. Fine, tough, bluish, stratified clay containing marine 
fossils, 1¢ feet (-4 m.) 
4. Boulder clay, 3 feet (-9 m.). 
5. Limestone rock in place, glaciated, striae, course 
Sy Oe oe 7 
Northeast of this locality, or toward Gatineau river 
the sections of the 1idges show waterworn boulders of 
smaller size and far more Laurentian pebbles than does 
the one just described. These deposits are spread out 
fanwise on an eroded surface of marine clay. 
These ridges have been described by Dr. Chalmers 
[5] and W. J. Wilson [7], and were considered by Dr. 
Chalmers to be due to both sea-borne and river ice. Mr. 
Wilson regaided them as possibly of morainic origin. 
On account of the unglaciated character of most of 
the boulders of the deposit, the imbricated position of 
the boulders suggesting current action, and the general 
absence of clay in the matrix, the more probable explana- 
tion of the occurrence of the ridges seems to be that they 
are due to 1iver deposition aided by ice action during a 
late stage of the marine submergence or at a time when 
the waters of the Ottawa and Gatineau iivers stood at a 
higher level than they do at present. 
Stratified sands and gravels overlain by boulder clay 
also occur in the Ottawa district and are hence regarded 
as interglacial in age. 
A good section of the upper boulder clay is exposed 
at the Canadian Northern Railway station, about one 
