36 JOURNAL OF THE 



bvoWfj^ht into it by streams. And since the ocean pro- 

 vides the gradual retardation of currents which make 

 their way into it, we have a perfect fulfillment of the 

 conditions of water sorting, and, hence, we may declare 

 the general rule that the coarser materials are depos- 

 ited near the shore and the finer out. Indeed, where 

 we find undoubted marine deposits including fragments 

 of large size such as grit or pebbles, we may reckon 

 with certainty upon the proximity of the sea shore 

 during the time when they were deposited. 



So then the presence in any region of such fragmen- 

 tal deposits as may be judged from their nature to be 

 niarijic declare unmistakably the presence there of the 

 ocean at such a date in geological history as our study 

 of these deposits may refer them to. For instance, if 

 we were to find in Western New Jersey marine deposits 

 of Cretaceous age, dipping g'ently eastward, we should 

 conclude that during the Cretaceous period the Atlantic 

 shore line lay west of that point. How far west it may 

 have stood we must determine by other means, perhaps 

 by actual shore marks, such as a wave cut bench, or a 

 series of beach gravels or sand dunes. Or else from 

 from the coarseness of the sediments near their inner 

 border we may conclude that they mark the actual 

 shore line of that period. 



Other processes of reasoning are often brought to 

 bear which cannot be dwelt upon within the narrow 

 limits of this paper. We should remember always 

 that such evidences as have been mentioned do not ne- 

 cessarily indicate the greatest amount of encroachment 

 of the sea within any given period, for deposits made 

 further inland may have been removed by the general 

 erosion of the surface: so also shore marks are compara- 

 tively seldom left as enduring monuments, and their 



