238 THE POPULAR SCIENCE MONTHLY. 



One can not see that this view better suits the facts than to suppose 

 there were two centers of dispersion, one for Greenland and the other 

 for the continent. From Greenland to the southwest edge of the gla- 

 ciated area the distance is twenty-five hundred miles, two fifths greater 

 than from the Laurentian highlands, and requiring a descent of over 

 seven miles of vertical elevation from the center to the circumference. 

 It seems unnecessary to add to the difficulties of height incurred in the 

 shorter distance. Provided there has been no great elevation of the 

 land, Davis' Strait seems to contain enough ocean-water to carry off 

 all the glacial products poured into it from either side. The facts of ice- 

 movement already stated for Labrador and the Arctic Archipelago show 

 motion easterly and northerly in the teeth of this imagined current 

 from Greenland. Hence, as we find phenomena of glaciation in agree- 

 ment with our view of radial dispersion from Labrador, whose exist- 

 ence was unknown to Torell, it seems as if it were altogether unneces- 

 sary to look so far as Greenland for the source of the ice-flow. 



Terminal Moraines. Years ago, those who believed icebergs 

 would explain glaciation triumphantly asked the glacialists, Where are 

 the terminal moraines which must have accumulated at the lower edge 

 of the great ice-sheet ? It is very strange their existence was not 

 suspected by the early glacialists ; and, as we now show their lines of 

 distribution upon our maps, we remove another obstacle to the accept- 

 ance of the glacial theory. 



Writers now generally employ the word till to denominate the ma- 

 terials accumulated by the ice, including the moraines and bowlder 

 clays. The ground-moraine is that form of the till least noticed in 

 the examination of active glaciers, because situated in the nearly im- 

 penetrable abysses between ice and earth. In the continental glacier, 

 where the surface had the unbroken white snow for its covering, this 

 form of moraine accumulation must have been the most abundant. 

 In middle New England the ground-moraine is developed into the 

 lenticular hill an oblong rounded hummock, sometimes two hundred 

 feet high, mostly composed of lower till, with a trend correspond- 

 ing to the direction of the ice-current in the neighborhood, varying 

 from nearly southeast near Newburyport to south 10 west in the 

 Connecticut Valley. This lower till is compact, sometimes clayey, full 

 of small, scratched, far-traveled stones in a forced position, with the 

 iron coloring matter in the ferrous or protoxide condition. The cap- 

 ping of the hill or upper till is loose, the fragments are rough, not 

 far removed from their source, commonly lying naturally, and the 

 color is yellowish red from the presence of ferric oxide. These char- 

 acteristics suggest the derivation of the upper till from the materials 

 held in the ice at the time of its melting ; they falling promiscuously 

 upon the surface of the ground-moraine, compacted by the great 

 weight of the glacier. 



The moraines regarded by us as terminal are in all respects like 



