328 Southern Cross. 



four miles south of the camp. According to his description, they 

 occur in small dykes three feet wide, traversing the cliff from top to 

 bottom at various angles. 



A large mass of basalt from Franklin Island is remarkable for 

 the number and large size of the olivine-enstatite nodules, such as 

 occur, e.^., in many of the basalts of Ehenish Prussia, and also in the 

 nepheline-basalts of Fernando Noronha. 



The rock in which these nodules occur approaches a limburgite : 

 it consists of a pale brown glass containing small idiomorphic olivines, 

 purple prismatic augites, magnetite grains, and only a few felspar 

 laths. 



The olivine-nodules are as large as the fist. In composition they 

 are precisely similar to those which have been described in other 

 basalts, and consist of a fairly coarse-grained aggregate of pale 

 greenish olivine, yellow enstatite showing polysynthetic twinning, 

 brilliant green chrome-diopside, and picotite. 



Specimens from Protection Cove, near Cape Cod, south of Eobert- 

 son Bay, present somewhat different characters to most of the other 

 basalts. They are more felspathic and altered, with vesicles filled 

 with calcite. Under the microscope they show fairly large and 

 numerous phenocrysts of labradorite with fine twin striations 

 (symmetrical extinction about 20°), in a dense brown glassy base 

 containing smaller felspars, some in laths, others in more isometric 

 forms. These specimens appear to have been collected near the 

 junction of the basalt with the slate, and are accompanied by tuffs 

 (see p. 330). One specimen shows basalt in contact with a mass of 

 green opaline silica, and under the microscope, besides this opaline 

 silica, are seen fragments of what appears to be altered slate, which 

 are inter-penetrated by the basalt. 



PHONOLITIC TRACHYTES AND KENYTES. 



Of these phonolitic rocks there are only three rolled fragments in 

 the collection. These probably came from Cape Adare, but no inform- 

 ation is forthcoming as to their connection with the basalts in the 

 field. The " trachyte " from Cape Adare, described by Prof David 

 {I. c. p. 473), with its abundant nigirine, is of a phonolitic type. A 

 phonolitic rock from Possession Island was also found in the Poss 

 Collection {I. c. p. 78). 



Of the present specimens one is of a dark greenish-brown compact 

 rock, showing small phenocrysts of lath-shaped felspar. Under the 



