306 AUGUST F. FOERSTE 



slightly the slopes on the two sides of the crests of the latter differ 

 in most cases. Frequently it is difficult to determine a difference 

 in slope at all, and rarely is this difference strongly defined, as in the 

 case of the strong ripples found after ebb tide along our present 

 coasts. 



Eventually it may be possible to accumulate sufficient evidence 

 to determine with considerable certainty the conditions under 

 which many of the strata of ancient days were deposited. To 

 many the evidence appears to be already at hand. To others a 

 revision of the evidence may appear necessary. To the writer it 

 appears desirable that those who have indubitable evidence of 

 land conditions during the deposition of Ordovician strata in the 

 states of the Ohio Valley should publish the same. This is true 

 especially in case of raindrop impressions and of mud-cracks, 

 which are favorite evidences locally of shore and land conditions 

 during Ordovician times. 



