THE CARBONIFEROUS SYSTEM. 107 



by the icebergs that come down from the far north freighted with these 

 materials, which are dropped into the water as the ice melts. 



I also have under my eyes as I write a suite of specimens dredged up 

 from the bottom of the ocean, off the Antarctic continent. These speci- 

 mens, and the report of the Exploring Expedition, teach us that this sea 

 bottom is every where strewn with pebbles derived from the neighboring 

 continent, and scattered by icebergs. Hence, from the similarity of the 

 deposits now being made by icebergs over various portions of the sea bot- 

 tom with those made by the same agency during the Drift period, and 

 of both to the materials composing the Carboniferous conglomerate, I 

 have suggested the possibility that they might all be the products of the 

 same agency ; that is, that the materials of the Conglomerate may have 

 been broadly and evenly distributed, as we find them, and subsequently 

 triturated, comminuted, and rearranged by shore waves when the water 

 was shallowed, and the surface was swept by tidal currents and storm 

 waves. In this view the Conglomerate should be compared with the 

 kames and eskers of the Drift. This theory, however, is not insisted 

 upon, but is simply a suggestion which has sprung from a conviction of 

 the entire inadequacy of any other solution of the problem yet offered. 

 In many places in Ohio we find in the Conglomerate sheets of pebbles, 

 many of which are two and three inches in diameter, and I have had 

 much difficulty in believing that these large pebbles were ever spread as 

 widely and evenly as they are by causes as local in their action as river 

 currents. Should it be proved by further investigation that the Con- 

 glomerate is the record of a glacial or iceberg period, it would account 

 for the occurrence of a similar deposit in the Old World; as the Conglom- 

 erate there holds the same place in the geological series, and is composed 

 of the same materials. It evidently marks a corresponding period in 

 geological time, and may have been deposited in an identical period in 

 absolute time, since we know that the phenomena of the Drift period 

 were similar in character and synchronous throughout the Drift area of 

 the northern hemisphere. 



Immediately succeeding the deposition of the Carboniferous conglom- 

 erate — we may perhaps say during the process of its accumulation — 

 the Carboniferous sea shallowed over a large area, and that which was 

 before sea bottom became dry land. In the retreat of the ocean waters 

 every portion of the surface they had covered would in succession be ex- 

 posed to the action of the retreating shore waves, and, as a consequence, 

 the surface materials would be shifted, sorted, and still further commin- 

 uted. Precisely similar influences operated upon the Drift deposits, to 

 which reference has been made, and the phenomena which they now 



