10 
KENDALL : THE OLACIER LAKES OF CLEVELAND. 
An aligned sequence is one in wliich several valleys may be 
obstructed, and drain from one to another by severed spurs, 
until free escape is offered either laterally or directly. These 
aligned series will all have their fall in the same direction, and 
the lake-levels will be successively lower along the series until 
the main escape is reached. 
In studying the severed spurs, with their variants, in an 
aligned sequence, no surprise need be felt if two spurs are severed, 
w^iile an intervening one of equal prominence remains intact. 
The ice-margin has commonly been very sinuous, and even lobate, 
and a lakelet might stretch across two valleys or more. Very 
often it has happened that an aligned sequence has been modified 
by a differential retreat of the ice-margin, causing one lake to 
persist longer than another. Thus a retreat of the ice-front 
near the lower end of a series may allow of a lateral escape and 
thus throw some intermediate channel out of operation, w^iile 
its neighbours, above and below, continue to fulfil their functions 
and to cut lower. 
The other kind of serial development I have termed a parallel 
sequence. These series, which frequently have also an align- 
ment, consist of repeated trenchings of the same spur by parallel 
overflows. They are produced by an intermittent retreat of the 
ice -front, uncovering successively lower slopes of a hillside. It 
is satisfactory in these cases to find that the level at which each 
overflow commences to be cut is below the intake-level of its 
antecedent. 
(4) In-and-out Channels. — These are crescentic valleys 
excavated in the face of a hill by water flowing round a projecting 
lobe of ice. 
These overflow channels display some striking peculiarities 
of form, which distinguish them from valleys of normal types. 
The flrst feature that strikes the observer is their entire 
independence of the natural drainage. They cut across the 
natural watersheds, and frequently are deepest just where they 
pass through it. This feature it is which appears most decisively 
to point, not merely to obstructed drainage, but actually to the 
existence of bodies of standing w^ater. 
