128 
MARINE DEPOSITs. 
Following the withdrawal of the last ice sheet a 
long arm of the St. Lawrence embayment extended far 
up the Ottawa valley. Marine sediments are widespread 
in the Ottawa district, and at many places shells of marine 
species are abundant in the sands and clays which were 
deposited during this submergence. To what height the 
district about Ottawa has emerged from the sea since 
the withdrawal of the ice, and how far westward the embay- 
ment extended have long been disputed questions. Marine 
fossils have been found at various places in the district 
to a height of 475 feet (144-7 m.) above sea level, but 
the upper limit of marine submergence has been generally 
put considerably higher. Baron de Geei in his determina- 
tion of the highest marine shore line near Kingsmere 
lake, a few miles north of Ottawa, placed the upper limit 
in the Ottawa district at 705 feet (215 m.) above sea level 
[2, p. 469]. Sir William Dawson [3, p. 294], Dr. Chal- 
mers [4, p. 68] and Dr. Ells [6 p. 222], all maintained 
that the minimum limit of submergence was at least 
1,000 feet (305 m.), and that the Pleistocene sea extended 
westward over the greater portion of Ontario. 
These views as to the extreme height of submergence 
were apparently based on the general similarity of the 
unfossiliferous sands and clays at high levels to the un- 
doubted marine sediments at lower levels and the occur- 
rence of waterworn gravel and transported boulders at 
high altitudes, rather than upon the determination of the 
height of any definite strand lines. 
Of late years comparatively little field work has been 
done in this district. Partly for this reason, partly because, 
as has been found in the lower St. Lawrence valley, the 
upper marine strand line is but faintly marked by wave 
built features and hence is difficult to locate with any 
degree of certainty, and partly owing to the widely diver- 
gent views held on the subject, it can only be stated that 
the upper limit of marine submergence near the city of 
Ottawa was not less than 475 feet (144-7 m.) and was 
probably higher, though there seems to be little evidence 
that it greatly exceeded this height. 
The highest point in the city of Ottawa is Parliament 
hill on which the parliament buildings are situated, and 
