CO THE JOURNAL OF GEOLOGY. 



process by which the basal material is carried upward the reverse 

 will not be the case, and there will be a clear distinction between 

 the englacial deposit and the subglacial deposit, in composition 

 as well as physical state. 



Not a few glacialists, however, advocate in somewhat differ- 

 ing forms and phases the doctrine that basal material is carried 

 upward into the body of the glacier and at length reaches the 

 surface, and that at the extremity of the ice this is commingled 

 with any erratics that may be englacial or superglacial by original 

 derivation. This doctrine appears to have had its origin in the 

 endeavor to explain the very common fact that glacial drift has 

 been carried from lower to higher altitudes. Erratics are often 

 found lodged several hundred feet higher than the outcrop from 

 which they were derived. It has never seemed to me, however, 

 that this phenomenon necessarily was different in kind from that 

 which takes place in the bottom of every stream ; at least I 

 have not come in contact with any instances that seemed to 

 require a different explanation, except those connected with 

 kames and eskers that require a special explanation in any 

 case. We are so accustomed to view streams from above, and 

 so accustomed to study the extinct glaciers from the bottom, 

 that we are liable to overlook the community of some of the 

 simpler processes involved alike in both phenomena. The 

 dictum that water never runs up hill is measurably true of the 

 surface currents of the ice as well as water, but it altogether 

 fails when applied to the basal currents of either. It is probable 

 that there is no natural stream of any length in which, at some 

 part of its course, basal debris is not carried from lower to 

 higher altitudes and lodged there. If the bed of any stream 

 were made dry and the debris in it critically examined, it would 

 be found that at numerous points the silts or sands or gravels 

 had been carried from the bottom of some basin in its bed to 

 the higher rim or bar or reef that bordered it on the down- 

 stream side. So I conceive that, on a grander scale, the natural 

 result of the flow of the basal ice of a continental glacier over 

 the inequalities of the country was the lifting of material from 



