THE METAMORPHIC ROCKS OF ADELIE LAND 8TILLWELL. 19 



permanently. In one case the ice was under observation for nine months and no move- 

 ment capable of measurement took place. The fourth and ice-free valley has the steepest 

 grade, and the sides are straight and in places steep, and, in a general way, indicate 

 glacial movement in the direction on the valleys. The valley walls which slope with 

 the dip are rounded and smooth, while those which slope against the dip are torn up 

 and ploughed very rough. Morainic material is in one case distributed laterally along 

 the walls, while the glacier ice itself is partly coloured by the presence of the subglacial 

 material. If valley glaciers of this type exist, a set of minor ice movements are intro- 

 duced subsequent to, and in a different direction from, the movements which produce 

 the striae observed N. 32 W. We were unable to pick up any trace of a second set of 

 striae, while in the lower part of one valley, where it opens out to a broad area, striae 

 can be seen trending in the constant direction N. 32 W. 



The upper limit of the subglacial material of the ice sheet (marked by a dotted 

 line on the locality plan) descends to lower levels at the head of valleys, suggesting 

 that morainic material has been pushed further on in the direction of the valleys. Hence 

 in spite of the absence of the second set of striae, secondary minor movements of the 

 valley glacier type are suggested. Such movement is negligible at the present time. 

 A combination of (a) and (b) may probably produce the present result. 



(c) Thaw Water Action. This is a possibility that suggests itself immediately to 

 one that has not visited the area. As above stated, thaw water action is, on the whole, 

 feeble. The lakes are thawed out only for two or three weeks during the year. The 

 character of the valleys is markedly not that produced by water streams. 



(d) Wind Action. The constant direction of the wind corresponds with the direction 

 of the valleys, and this fact suggests wind-scoured depressions. The unsymmetrical 

 and varying slopes on the valley walls are hardly consistent with the hypothesis, as the 

 rock is of uniform hardness. Further, the undercutting, which is so characteristic of 

 wind erosion, is, in the main, absent. An odd boulder shows wind erosion, but only in 

 one small spot in situ did we observe undercutting. The rocks are remarkably fresh 

 and unweathered, and the lapse of time since their uncovering cannot be great, and 

 cannot be sufficient for wind excavation of the valleys. 



(e) Pre -glacial Strike Valleys. This theory will be accepted if all other possibilities 

 are rejected. At present the short shallow valleys possess nothing that suggests water 

 action. All such traces might disappear in the subsequent modification of the valleys 

 during glaciation. 



MORAINES. 



Not only is our small area sprinkled with erratics, but also well marked moraines 

 have been left by the retreating ice front in more or less parallel banks. These moraines 

 are entirely the product of the basal load of the glacier. No surficial or interglacial 

 material is present in the terminal section. 



