78 DISCOVERY REPORTS 



On the other hand, the rocks of Lookout Harbour at the extreme south are of markedly different 

 mineral composition and metamorphic grade. According to Tilley they are divisible into three 



petrographical groups: 



(a) Garnet-hornblende-albite-schists, 



(b) Amphibole-bearing marbles, 



(c) Para-amphibolites. 



The rocks of these three groups are linked by the general presence of hornblende, and, to a less degree, 

 albite. Their study, aided by chemical analyses, leads to the conclusion that 'they form a graded 

 series of related sediments ranging from limestones to impure types giving the amphibolites and 

 garnet-hornblende-schists rich in albite'. The original sediments were of abnormal composition, 

 inasmuch as abundant albite was present, probably derived from detrital plagioclase. The grade of 

 metamorphism is obviously much higher than that of the northern phyllites. No data are given of 

 the attitude or geological structure of the Cape Lookout series, which may occupy the southern half 

 of Elephant Island. 



CORNWALLIS ISLAND 



This is a small island lying in the strait between the much larger Elephant and Clarence Islands. 

 There is no record of a landing, and nothing is known of the geology except a brief note by Mr Ferguson 

 (op. cit. supra, p. 35). He says: 'It was not possible to land, but the steamer got very close in. It 

 [Cornwallis Island] rises sheer out of deep water in splintery crests, and is partly covered with snow. 

 The highest point of the island may be 1000 ft. or more above sea level. The slopes are very steep, 

 often quite vertical, and there is consequently much bare rock. ... It is formed of light-grey schistose 

 rocks, the foliation planes having a direction [of strike] about N. 70-80" E., with a nearly vertical 

 dip.' Cornwallis Island is not far to the east of Cape Valentine on Elephant Island, where Wordie 

 recorded the strike as east by north, i.e. about the same as that of the rocks on Cornwallis Island. 

 Wordie also says that 'the mountains along the coast [of Elephant Island], when of bare rock, have 

 precipitous slopes and serrated crests of the "frayed cardboard edge" type', which agrees well with 

 Ferguson's description of the topography of Cornwallis Island quoted above. It may therefore be 

 taken as probable that Cornwallis Island represents an eastern continuation of the same rocks as 

 those of the northern coast of Elephant Island. 



CLARENCE ISLAND 



So far as is known, no geologist had landed on Clarence Island until Prof. O. Holtedahl, in January 

 1928, managed with some difficulty to get ashore near the northern point (Cape Lloyd) during the 

 Norwegian Antarctic Expedition of 1927-8.^ But Ferguson, during the Salvesen Expedition of 1913, 

 passed close enough to Clarence Island to make a few observations {op. cit. supra, p. 36). He says: 

 ' The north-east coast is a wall-like rampart, 500 ft. or more in height, of very regular and well-bedded 

 rocks, light grey, dark grey, and drab coloured. The west coast shows light grey, finely banded rocks 

 with a nearly vertical dip in places, and a broad band of brownish rock, evidently an intrusion, was 

 seen at one place cutting through them.' This description agrees well with Holtedahl's and with 

 photographic views of the north-western coast of Clarence Island published by Holtedahl {op. cit. 

 pis. xxiii, xxiv). 



As regards the rocks, Holtedahl collected a number of characteristic specimens from the scree at 



1 O. Holtedahl, 'On the Geology and Physiography of Some Antarctic and Sub-Antarctic Islands', Scientific Results of the 

 Norwegian Antarctic Expeditions of 1927-8 and 1928-9, instituted and financed by Consul Lars Christensen, No. 3, Norske 

 Vidensk.-Akad., Oslo, 1929, 172 pp. (Clarence Island, pp. 47-8). 



