g2, DISCOVERY REPORTS 



be regarded as due to low-grade metamorphism of basaltic rocks of this type. Its association with 

 quartz veins, and with a quartzite-like rock, and its chemical and mineralogical similarity to the 

 prasinitic schists of Tierra del Fuego and Clarence Island, make it congruous with the whole 

 assemblage of rock types found in the Scotia Arc, and adds confirmatory evidence for the theory of 

 tectonic connexion between South America and West Antarctica favoured by E. Suess and other 

 writers (see this Memoir, p. 89). 



PARTY. PETROGRAPHY OF THE SOUTH SANDWICH ISLANDS 



INTRODUCTION 

 The volcanic South Sandwich Islands are situated at the extreme eastern end of the Scotia Arc, and 

 form either a part of it, or a volcanic arc parallel to 

 and in echelon with it. They are fully described in 

 a recent publication to which reference will be fre- 

 quently made in the ensuing pages. ^ It is proposed 

 in this paper to summarize and collate the already 

 published petrographic data, and to supplement 

 them with descriptions of new material from five 

 localities, viz. material collected in situ by Mr G. 

 Rayner on Saunders Island, and dredgings from 

 four stations: (i) St. 363, 2-|- miles S. 80" E. of the 

 south-eastern point of Zavodovski Island, (2) St. 

 366, off the south coast of Cook Island, (3) St. 368, 

 in Douglas Strait between Cook Island and Thule 

 Island, (4) St. 370, 2 miles north-east of Bristol 

 Island. In addition, there are some stones collected 

 from a piece of floating ice near Bristol Island. 



Many observations on the volcanology and on 

 the rocks of the South Sandwich Islands as seen 

 from a distance are published in the above memoir, 

 but the only petrographic data so far published are 

 to be found in the following three papers: 



(i) O. Backstrom. ' Petrographische Beschreibung 

 einiger Basalte von Patagonien, Westantarktika, und 

 den Siid-Sandwich Inseln', Bull. Geol. Inst. Upsala, 

 XIII, pp. 115-82 (1915). South Sandwich Islands, 

 pp. 163-76. 



(2) G. V. Douglas and W. Campbell Smith. 

 ' Zavodovski Island, and Notes on Rock Fragments 

 dredged in the Weddell Sea ', ' Quest ' Exped. Report 

 {Brit. Mus. Nat. Hist.), pp. 63-7 (1930). 



(3) G. W. Tyrrell. ' Report on Rock Specimens 

 from Thule Island, South Sandwich Islands', 

 South Sandzvich Islands Memoir, pp. 191-7 (193 1). 



1 Stanley Kemp and A. L. Nelson, 'The South Sandwich Islands', Discovery Reports, in, pp. 133-98, pis. xi-xxxi (1931). 

 Hereinafter referred to as South Sandwicti Islands Memoir. 





Fig. 14. The South Sandwich Island. 



