WILLIAM B. DWIGHT, ST 



This Quaternary clay belongs to the fluvial and lacus- 

 trine formations of that period, which, in the language 

 of Prof. J. D. Dana, "appear to characterize all the 

 river valleys and lake-basins of the continent over the 

 drift latitudes and also, to a lesser extent, those still 

 farther south ; so that they may be said to have a con- 

 tinental distribution." 



It is supposed to have been formed mainly during the 

 second or Champlain division of the Quaternary. The 

 elevated lands of our more northern latitudes, covered 

 by a vast southward-moving ice-cap, in the first or 

 glacial era, had sunk five hundred or one thousand feet. 

 It was an era of great floods, and expanded lakes and 

 rivers. The debris of melting glaciers, and of decom- 

 posed and eroded rocks, was deposited — sometimes under 

 violent action of the waters, sometimes under gentler 

 currents — all along our great lakes, and all the water- 

 courses over this part of the continent. During the 

 earlier epochs of these great transportations of earthy 

 material, when the waters had not yet accumulated suf- 

 ficiently to re-arrange the drippings of the melting 

 glaciers, the deposits were unstratifled and unsorted. 

 But when the increasing waters took up the droppings 

 of the glaciers, the material was at once redeposited in 

 successive layers of stratification, while the coarser and 

 finer portions were laid in somewhat separate courses. 



Both banks of the Hudson, for the greater part, at 

 least, of its length, are lined with beds of clay thus' 

 formed, and in many cases extending to quite a dis- 

 tance inland. During the following, or Terrace Period, 

 an elevation of land took place, which has lasted until 

 the present time. As the result of this elevation, the 

 diminishing waters have cut down their channels through 

 these deposits, also narrowing their banks during suc- 

 ceeding epochs ; thus leaving the successive terraces on 

 which the river cities repose. 



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