330 POPULAR SCIENCE MONTHLY. 



of tide water, and almost every essay differs in more or less degree 

 from its fellows in the matter of the gravel's age as a well-defined 

 deposit. Its origin no one can question, nor the agencies by which 

 it was brought to where we now find it. Ice and water did the 

 work, nor have they ceased entirely to add to the bulk transported 

 in strictly glacial times perhaps it were better to say in superla- 

 tively glacial time, as the river even now can be positively glacial 

 upon occasion, as Fig. 2 demonstrates. The main channel has often 

 been completely blocked with ice and the water forced into new 

 directions and spread over the lowlands or flats, which it denudes 

 of its surface soil, and once within recent years the stream found 

 an old channel, deepened it, and for a time threatened to leave a 

 flourishing riverside town an inland one. Ice accumulated in this 

 way year after year must necessarily affect the river's banks, and 

 yet the extent of " damage " is trifling usually, in comparison with 

 that of the water, particularly when agitated by passing steamboats 

 or violent winds; and now, too, the ice of our present winters does 

 not transport coarse pebbles to any significant extent. I am con- 

 vinced of this since the examination I gave acres of ice, when the 

 river was gorged with it, some years ago. It was possible to walk 

 for miles over the ice, as shown in Fig. 2, and to see it under exceed- 

 ingly favorable circumstances, and a most careful search failed to 

 reveal a stone larger than a pigeon's egg incased in this ice, which 

 was all gently floated from far up the stream and stranded here ; and 

 where piled up upon the shores it usually remains until melted, and 

 really acts as armor plate, protecting the ground from abrasion 

 when the floods incident to the " break-up " prevail. Such are the 

 present-day considerations, and they have a direct bearing upon the 

 question of man's antiquity here because, first, the river valley has 

 not varied for hundreds of years, except in becoming wider, the 

 low shores receding, and the stream becoming broader and more 

 shallow. In earliest Indian times the river was subject to freshets 

 and ice gorges as now, but never did the water become so dammed 

 up as to overflow the broad plateaus, areas of glacial gravel, that 

 at the close of the Glacial period were within the boundary of the 

 river. The Delaware was a very different stream then crescendo 

 for thousands of years, and diminuendo for thousands since until 

 now it barely hints at what once was. But not even in the height 

 of its glacial activity was the climate so severe that the waters con- 

 tained no fish, nor the forests of the high surrounding hills harbored 

 no game. Never was it as bleak as the arctic region of to-day, and 

 as man maintains a footing there, why should he not have done so 

 here, where life was ever more easily sustained? True; but did he 

 live here in glacial time? 



