6 GEOLOGY. 



has been thought to call for some exceptional means of transporta- 

 tion. On this ground, it was long since conjectured that it was formed 

 at a time when glaciers existed in the eastern part of the United States. 

 Furthermore, glacial action, if operative in regions where there was 

 limestone, might produce conglomerate comparable in constitution 

 to that here found. It should be noted, however, that it was the 

 supposed demand for some exceptional agent of transportation, rather 

 than any direct evidence, which suggested the existence of glacier 

 ice. The constitution of the conglomerate at most points, and especially 

 the characteristics of its constituent parts, do not seem to support the 

 suggestion. In general, the materials are too well assorted to be the 

 immediate product of glaciation, and the stones and bowlders are 



Fig. 309. — Diagram showing how the limestone which gives rise to the conglomerate 

 might have been removed by erosion, leaving some of the limestone conglomerate. 



not only not striated, but generally possess forms not characteristic 

 of ice- worn bowlders. These objections to the hypothesis of the glacial 

 origin of the conglomerate lose much of their force if the formation 

 be looked upon as a deposit in water to which glacial drainage con- 

 tributed; but in the absence of all certain evidence of glacial or glacio- 

 fluvial origin, it seems more prudent to regard the conglomerate as 

 an exceptional phase of a shore formation. 



The sandstone and shale. — The great body of the Newark series 

 is sandstone and shale, and both possess three or four notable charac- 

 teristics. First, their prevalent color is red, though there are shales 

 which are black, and sandstones which are gray. Second, except 

 locally, the series is poor in fossils, and those which exist are of such 

 a character as to indicate that the beds were not accumulated in open 

 sea-water. Third, some of the sandstone contains a considerable 



