8 
MUSEUM BULLETIN NO. 24. 
The altitudes are all in feet above sea-level and are, with the 
exception of the last two, based on precise levels; that is, the 
altitudes were determined by levelling to or from the water-level 
of Lake Deschenes or the expansion of the Ottawa river above 
the lake proper, the altitude of which at the time was determined 
from bench-marks established by precise levelling done by the 
Department of Public Works. The last two altitudes were 
Figure 1. Raised beaches in the Ottawa valley, showing altitudes in feet 
above sea-level, and isobases, 
determined by levelling from road corners, the altitudes of which 
were determined by levelling done by the Department of Militia 
and Defence. 
The shore-line of a portion of this lake is shown on the accom- 
panying outline map. Altitudes of the shore-line in feet above 
sea-level and isobases at an interval of 10 feet are also shown. 
