RECENT AND FOSSIL RIPPLE-MARK. 
S3 
rents coming to the shore line from a different angle as no two 
are parallel. On one of the slabs collected there are worm 
tracks and several impressions of a horse-tail rush.” As already 
stated the symmetry of these ripple-marks shows that they are not 
current but wave made. Mr. Brown would have been correct if he 
had stated that they indicate winds of varying direction rather 
than currents. 
At other levels in these beds asymmetrical ripple-mark 
has been found by Mr. Sternberg which indicate current action. 
PAL^EOGEOGRAPHIC SIGNIFICANCE OF RIPPLE-MARK. 
In formations which are very generally ripple-marked 
throughout careful tabulation of the general trend of the ripple- 
mark may afford important evidence regarding the position of 
shore-lines at the time of their formation. Symmetric or wave- 
made ripple-mark if found in water of moderate or slight depth 
will trend approximately with the shore off which it was formed. 
Asymmetric or current ripple-mark (Plates XXVII to XXIX) will 
trend at right angles to the course of the current which produced it. 
In the case of tidal currents the direction of the current is generally 
parallel to the nearest shore. Hence the asymmetrical ripple-mark 
produced by them trend at right angles to adjacent shore-lines. 
Fossil asymmetrical ripples thus indicate a shore-line trending at 
right angles to their course while symmetrical ripples indicate a 
shore-line parallel to their own direction. It is, of course, evident 
that any trustworthy deductions of this kind must be based 
upon a large number of observations. 
Prof. Jesse E. Hyde has made effective use of this kind of 
evidence in his study of the ripple-mark in the Bedford and 
Berea formations. His deductions regarding the trend of the 
shore-line, based upon the observed constancy of direction of the 
ripple-mark, are indicated in the following extract from his paper : 1 
“The conclusion seems to be warranted that the persistency 
of direction of the ripples of the Bedford and Berea indicates the 
prevailing direction of the water waves which formed them and 
that this in turn was controlled, either by a shore line or water 
so shallow as to bring the waves into adjustment parallel to this 
i Jour. Geoi., vol. XIX, No. 3, April-May 1911, p. 26S. 
