SCIENTIFIC ADVANTAGES OF AN ANTARCTIC EXPEDITION. 423 



past — geology, mineralogy, volcanic action under special conditions — 

 all of these are subjects on whicli the phenomena of the Antarctic 

 regions are sure to bear directly. 



If, however, I am asked to specify more particularly the question on 

 which I look for invaluable evidence which can be got nowhere else, I 

 must name, above all others, the most difficult questions involved in 

 quaternary geology. Geologists are nearly all agreed that there has 

 been, very recently, a glacial age — an age in which glacial conditions 

 prevailed over the whole northern hemisphere to a much lower latitude 

 than they prevail now. But geologists differ widely and fundamentally 

 from each other as to the form which glacial agencies took during that 

 period. In particular, many geologists believe in what they call an 

 ''ice sheet" — that is to say, in the northern world having been covered 

 by an enormous mass of ice several thousand feet thick, which, as they 

 assert, "flowed" over mountain areas as well as over plains, and filled 

 up the bed of seas of a considerable depth. Other geologists disbelieve 

 in this agency altogether. They deny that even such a body of ice ever 

 existed ; it could not possibly have moved in the way which the theory 

 assumes. They affirm, also, that the facts connected with glaciated 

 surfaces do not indicate the planing down by one universal sheet of 

 enormous weight and pressure; but, on the contrary, the action of small 

 and lighter bodies of ice, which have acted partially and unequally on 

 different surfaces differently exposed. 



We might have hoped that this controversy could be settled by the 

 facts connected with the only enormous ice sheet which exists in the 

 northern hemisphere, viz, that which covers the great continent of 

 Greenland. But that ice sheet, enormous though it be, does certainly 

 not do what the ice sheet of the Glacial Age is supposed to have done. 

 That is to say, it does not flow out from Greenland, fill the adjacent 

 seas, or override the opposite coasts, even in so narrow a sheet as 

 Smith's Sound. But this evidence is negative only. In the Antarctic 

 continent we have reason to believe that there is a larger ice sheet, and 

 it certainly does protrude into the adjacent seas, not merely by sending 

 out broken, floating fragments, but in unbroken ice cliffs of great height. 

 Now, we want to know exactly under what conditions this protrusion 

 takes place. Dr. Murray speaks of it as "creeping" seawards — a 

 more cautious word than "flowing." But is it certain that it does 

 even creep ? May it not simply grow by accretion or aggregation till it 

 reaches a dejDth of water so great as to break it off' by flotation"? Does 

 it or does it not carry detritus when no detritus has been dropped on 

 its surface? Or does it pick up detritus from its own bed? Or does 

 it push foreign matter before it? Does the perfectly tabular form of 

 the Antarctic icebergs indicate any differential movement in the 

 parent mass at all; or does it not indicate a condition of immobility 

 until their buoyancy lifts great fragments off"? What is the condition 

 of the rocks on which they rest? Is there any thrust upon the mass 



