226 GEOLOGY. 



there a wind deposit, and lie extends tbis explanation to the loess in the 

 valleys. Pumpelly, who has also had opportunity to see these deposits 

 in the dry steppes of Asia, has agreed with von Eichthofen, but his dis- 

 cussion of the question and the application of the theory to the formation 

 in the Mississippi Valley, incited dissent from Winchell, Hilgard, Broad- 

 head, and Todd, all of whom are familiar with the formation in the Mis- 

 sissippi Valley, and who all agree that no aeolian hypothesis will explain 

 the accumulation of this material, and they consider that the facts show 

 that it was gathered in quiet fresh waters, though salt-water shells are 

 not entirely absent. They show that the Mississippi formation is iden- 

 tical with that in the Rhine Valley, and possesses all its strange pecu- 

 liarities, and that hence this river valley formation was not made of 

 drifting sands anchored by grass, such as accumulates upon the steppes 

 and deserts. 



DRIFT. 



Another of the great unsettled problems is the origin of the drift 

 that is, there still remain advocates of opposing theories. Credner does 

 not hesitate still to refer the drift that covers our northern lands to the 

 action of floating ice, nor is he alone in his opinion. Mr. Upham, who 

 worked uj)on the surfoce geology in Xew Hampshii'e, in connection with 

 the geological survey, has traced what he considers the terminal 

 moraine of the great glacier sheet that covered the northern portion of 

 America, almost across the country. He finds this terminal moraine 

 stretching along Long Island, westward across New Jersey, and thus 

 onward. He finds remains as well of a second parallel moraine, far- 

 ther to the north, which marks a stage in the retreat of the glacier. 

 It is worth remarking that the drift deposits which cover the extensive 

 Xorth German plain have been subjected to much and careful study 

 during this period. The character of the bowlders, which are largely 

 identical with Scandinavian and Finland rocks, have been much studied, 

 and those works which have attracted most attention, notably that of 

 Berendt, do not attempt to explain all facts by referring them all to an 

 unyielding system. Rather, the facts tend to confirm a belief in the 

 alternations of the action of floating ice and glacier, and distinctions 

 l5etween the undoubted action of the one and the other are clearly rec- 

 ognized. By Mr. Upham, as by most recent students, the eftects iu 

 America have been mostly referred to the action of an immense glacial 

 sheet, with local tributaries, and to the rush of waters attendant upon 

 the melting of this body of ice. 



COAL. 



Small deposits of coal have been found in various geological horizons 

 lower than the carboniferous. For example, anthracite of silurian age 

 occurs on the Isle of Man, and is supposed to have been formed from 

 an accumulation of algie. It has been found in the graptolite bearing 



