part 2] MODE OF TBANSPOETATION BY ICE. 01 



About 50 miles farther south another wide bay opens, originally 

 called Terra Nova Bay. Its southern edge is formed by the long- 

 floating mass of the Drygalski Glacier- tongue between which and 

 the northern t'dge is a low sheet of iee formed by the confluence of 

 several glaciers and held in by sundry islands and shallows. This, 

 is the Nansen Sheet, and it is probably not more than 200 feet 

 thick, except where the glaciers directly flow into it. 



Still sailing southwards along the coast, we meet only with 

 glacier-tongues until the southern end of McMurdo Sound i* 

 reached, where a similar sheet formed by the confluence of glaciers 

 blocks the way round Koss Island. 



These sheets are all more or less completely afloat, and the two 

 last-mentioned are covered to a great extent with morainic debris. 

 The most important point of similarity is their slow rate of move- 

 ment — proved in the case of the two where the deposits have been 

 found, and inferred from our small knowledge of the northern one. 

 To regard them as remnants of the Great Ross Barrier is hardly 

 accurate, for (although they are stagnant) they are not wasting 

 very rapidly, and have very definite sources of growth. 



The raised deposits all present the following features in 

 common : — 



(a) In each case they are found resting on ice. with the solitary exception 



of the one at the mouth of Dry Yallej*. 



(b) In each case the organisms appear to have been preserved from shock 



or movement, and from prolonged atmospheric weathering. 



(c) The organisms in many cases are preserved in the position of growth, 



and have been raised without tilting or disruption. 



(d) They occur at all distances from the edge of the land-ice up to 



15 miles. 



(e) Their height above sea-level varies between 5 and 35 feet, except those 



at Cape Eoyds. which approach 200 feet in altitude. 



Theories as to the Mode of Origin of the Deposits. 



The only serious attempt at an explanation of these phenomena 

 hitherto made is that given by Prof. David & Mr. Priestley in 

 the Geological Memoir of the 1907 Expedition. In that closely- 

 reasoned account they make the best possible use of the evidence 

 then at hand, and finally discard the theory that the deposits are in 

 any sense 'raised beaches," always excepting the occurrence at Dry 

 Valley, which has features at variance with the ethers. 



The above-named writers then offer alternative theories, with 

 neither of which are they completely satisfied. Comparing the 

 deposit on the Nansen Sheet, below Mount Larsen, with those in 

 Spitsbergen described by Mr. Gr. W. Lamplugh, they suggest that 

 the sea-floor may have been ploughed up by the ice of the glacier 

 during an aecession after a temporary retreat. Undoubtedly the 

 Seftstrom Glacier in Spitsbergen has done so, though that action 

 does not seem to explain all the shelly moraines of Cora Island. 

 Put, in the case of the Mount-Larsen deposit, many miles from 

 the front of the iee. a ploughing action cannot very well be con- 

 ceived. The ditficultv is still further increased by the fact that 



