False Bedding in Stratified Drift Deposits, — Spurr. 45 
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Fig. l.—o,6, c, Successive ripple-marked layers of sediment. Scale, one inch to a foot 
third c, and so on. Tims, every point of the ripple-mark 
moves onward and upward, at an angle with the bottom de- 
pending upon the velocity of the current and the rate of dep- 
osition, — in this case about forty degrees. The dotted lines 
represent the direction of this upward advance. 
As the materials varied in point of size and weight, tin- 
larger fragments generally came to rest in the trough on the 
leeward side of the ripple-mark, that being the position where, 
owing to the shelter of the ridge, the current exerted least 
force. This happened with every fresh ripple-marked sur- 
face, and this trough (represented by A in the diagram), 
moving onward and upward, formed the layers of coarse ma- 
terial, which alternate with the liner sand of the gently slop- 
ing side of the ridge. Often these layers extend ten or twelve 
feet with perfect regularit}^. The real bedding, when not ob- 
scured, might easity be mistaken for a minor cross-bedding. 
What material was deposited on the gently sloping side of 
the ridges was more exposed to the pressure of the currenl 
than that accumulated to the leeward; and the deposition be- 
ing slower there, it was exposed much longer. Thus it became 
firmly packed. When laid open to the weather, as in this 
cut, these layers stand out ridgewise, while the looser and 
more rapidly formed parts are worn away. This high tens the 
deceptive appearance of stratification. 
The process of accumulation is explained in figure '2. ;i dia- 
gram made from a sketch. The ripple-mark may lie divided 
into three separate portions, where by accumulation are 
formed three distinct layers in the false bedding: I. the 
hollow immediately in the lei' of tin- Steep Bide, in which ac 
