I.j GEOLOGICAL OBSERVATIONS 329 



trachytic rock, but owing to lack of time a specimen was only 

 obtained from an off-shoot of this huge boss of rock. The northern 

 end is comparatively low, and the bright red areas around small 

 conical depressions point to the presence of scoria cones similar to 

 those at Winter Quarters. 



The Dailey Islands are fine small conical masses surrounded 

 by the ice in the middle of McMurdo Sound. Only one of these — 

 the largest— has been visited, and the usual scoriaceous basalts 

 were procured. 



The Dellbridge Islands, situated near the base of Mount 

 Erebus, have supplied a rather surprising variety of rocks. 



Razor Back consists of a vesicular basalt which is very much 

 contorted and locally is scoriaceous. 



Tent Island has an exposure of about 100 feet of conglomerate 

 on the steep north-west face. The upper part of the island consists 

 of sheet on sheet of basalt, making up a thickness of about 200 

 feet. These sheets dip at an angle of about 15 to the S.E. and 

 mainly consist of red basalt glass with lenticular crystals of 

 feldspar. 



Inaccessible Island was visited by Mr. Hodgson, and the 

 specimens he obtained include tuffs, vesicular basalts, and 

 trachytic rocks. He tells me the rocks are all very confused, 

 but generally dip to the north at an angle of about 40 . 



The Volcanic Cones on the Mainland. 



Four or five perfect cones, quite undenuded, stand at intervals 

 along the coast of South Victoria Land, and form a very striking 

 contrast with the comparatively unbroken outline of the mountain 

 ranges that abut on the Ross Sea. There are one or two other 

 cones which need not be considered, such as that on the summit 

 of Cape Jones, but all are isolated and do not form, as was 

 previously supposed, a continuous belt. 



Mou?it Brewster, probably only 4,000 feet high, is situated near 

 Lady Newnes Bay, and is important as it obviously does not 

 belong to the high land which rises to heights of over 10,000 feet 

 on the west of it. This small mountain is an almost perfect dome, 

 and has a slightly flattened summit. It rises rather suddenly 

 from the low foothills at the base of the great Admiralty Range, 

 and the snow-covered curves differ essentially from the com- 

 paratively bare precipitous cliffs of that range. 



