144 TRANSACTIONS OF THE CANADIAN INSTITUTE. — [Vov. VIII. 
Cross Section.—Fig. 6 is a diagrammatic section showing at one view 
the outline ABC of the lower valley or ravine while DEF is similarly the 
outline of the upper or thrown-down portion of the valley. This section 
is intended to represent the state of things upon the line of fault crossing 
the valley. The portion HEG of the upper valley is represented as filled 
with alluvium; while the portion KBL, only of the lower valley is so filled. 
HKLG represents the surface of the valley bottom above the fault, while 
below the fault the width of the valley bottom is reduced to KL. 
Fg. 6. Gofe Weehor ef Vibley ub Line of Fault 
E 
Plan.—Fig. 7 is a plan taken at the level of the bottom of a valley. 
It shows from a birds eye point of view the sudden reduction in the width 
of the valley at the line of fault indicated in the preceding diagram (Fig. 6) 
HG is the width of the valley bottom above the fault while KL is the 
width of the valley bottom below the fault. 
Actually no such regularity obtains as is shown in these diagrams. 
Practically the reservoir is of extremely irregular figure and composition; 
the irregularities and the sinuosities of its outline all add to its storage 
