86 
the glaciers, and doubtless, in part too, within the ice that 
floated away as icebergs. This fine mud was laid down 
upon the floor of the sea. Recurrent slight differences 
in its composition gave rise to a fine lamination which 
can often be seen in exposures of Leda clay, as these 
marine sediments are called. The shells found in the 
clay indicate that the climate of that time was similar 
to the present climate of the Labrador coast. At Green’s 
creek, near Ottawa, the clay is rich in calcareous nodules 
which have yielded many fossils, especially Mallotus 
villosus, (Cuvier) and other fishes. 
The Leda clay is overlain by the Saxicava sand which 
was laid down as the sea shallowed and withdrew to its 
present level. The Saxicava sand is often crowded with 
shells of Saxicava rugosa, Lamarck, though extensive 
areas may be examined without discovery of a single 
shell. That the emergence of the land took place in stages 
is shown by the successive terraces of the lower St. 
Lawrence, nowhere better shown than on the flanks of 
Mount Royal, where as many as seven raised beaches, 
indicating successive halts in the gradual elevation of 
the land, have been recorded by Sir J. W.Dawson [24]. 
The most conspicuous of these seen in passing along the 
Ottawa valley is the 220 foot (67 m.) terrace, known 
at Montreal as the Waterworks terrace. It is constantly 
in view, especially to the north of the railroad. 
Mier ANNOTATED GUIDE. 
Kilometres. 
0-0 m. Montreal (Place Viger)—Alt. 57 ft. (17-4 m.). 
12-8 m. St. Martin Junction—Alt. IIo ft. (33-5 m.). 
205 km. 
32-5 m. Ste. Scholastique—Alt. 238 ft. (72-7 m.). 
52-0 km. 
44-2 m. Lachute—Alt. 229 ft. (69-7 m.). 
70:8 km. 
57:6 m. Grenville—Alt. 210 ft. (64 m.). 
92-0 km. 
7Oo mi: Papineauville—Alt. 149 ft. (45-5 m.). 
126-8 km. 
83-9 m. Plaisance—Grenville limestone is exposed in 
134:3 km. the railroad cutting west of Papineauville. Be- 
vond this a granulite batholith, composed in part 
