133 
mile (1-6 m.) southeast of the Parliament buildings. 
The principal feature of the boulder clay is the quantity 
of large limestone boulders which, unlike those of the 
Hull deposit, are rounded and show marks of strong 
glaciation. The matrix in which the boulders are imbedded, 
although very sandy, is stiff enough to sustain the material 
in a perpendicular face. The boulder clay, which is over- 
lain by a few feet of yellow stratified sand, includes layers 
of irregularly bedded sands which appear to divide the 
boulder deposit into two sheets. 
A sand pit on the south side of Rideau river about, 
one mile (1-6 km.) southwest from the Canadian Northern 
Railway station, exhibits an excellent section of irregu- 
larly bedded sands and gravel overlain by the upper 
boulder clay. The boulders are much smaller and better 
rounded in the boulder clay of this deposit than in the one 
last described, and the quantity of clay in the matrix 
is greater, but it is a more friable deposit than the lower, 
older sheet. The variation in bedding and the alterna- 
tion of material in the underlying sands and gravels at this 
locality are remarkable, and they are said to be at least 
30 feet (g-I m.) in thickness. 
DRAINAGE FEATURES. 
The principal drainage features of the district may 
be explained briefly as follows :— 
The Ottawa river in the vicinity of Ottawa flows in 
an easterly direction at the base of the limestone escarp- 
ment fronting the old land to the north, and occupies 
a post-glacial channel in the sense that the probable pre- 
glacial course of the Ottawa or its predecessor was several 
miles to the south, where well borings show the presence 
of a broad, deeply drift-filled valley. The limestone 
escarpment, however, is believed to be for the most part 
pre-glacial in origin and due to stream erosion through 
a protracted period in pre-glacial times. 
In post-glacial time it is probable that the Ottawa 
river has cleaned out and somewhat deepened the old valley 
in the vicinity of Ottawa, and the steepwalled gorge which 
extends for a short distance below the Chaudiére falls 
is evidently due to post-glacial erosion. 
Rideau river, coming from the south, occupies a 
shallow post-glacial valley, flows across the old drift 
