326 Southern Cross. 



from Cape Adaie consists of a fragmental aggregate of sub-angular 

 grains of quartz and a little felspar with shreds of muscovite and 

 green altered biotite : deep red doubly-refractive grains of rutile 

 and rounded grains of zircon are also present. 



A specimen from Geikie Land is nearly colourless, as it contains 

 very little chlorite. Besides angular grains of quartz showing undu- 

 lose extinction, it contains grains of twinned oligoclase in a paste of 

 what appears to be secondary quartz, with shreds of muscovite and a 

 little chlorite. 



The fragmental material of these grits has probably been derived 

 from granitic or cneissic rocks. 



BASALTS. 



These rocks are for the most part fine-grained, compact, glassy, 

 hornblende-basalts, similar to those from Cape Adare and Possession 

 Island in Mr. Borchgrevink's earlier collection, and in the Boss 

 collection, which have been previously described. They contain 

 small phenocrysts of basaltic hornblende, undergoing reabsorption, 

 and often only represented by pseudomorphs of magnetite and augite, 

 in a deep brown glassy base of sharply-defined felspar laths, grains 

 of magnetite, minute rhombic sections of olivine, and a little augite 

 (see PI. LIIL, fig. 5). Only rarely is a much corroded phenocryst of 

 felspar seen in these rocks, and small pale purple augite phenocrysts 

 accompanying the hornblende are only present in some specimens in 

 small amount. 



Basalts of this character come from Coulman Island and from 

 the foot of Mount Terror, as well as from Cape Adare and Possession 

 Island, and all proljably belong to contemporaneous and recent flows. 



A chemical analysis of the hornblende-basalt from the foot of 



Mount Terror gave the following result : — 



BiO, =47-40 

 TiO^ = 0-63 

 AI.P3 =20-27 

 FeA = 5-38 

 FeO = 5-48 

 MnO = 0-17 

 CaO = 7-59 

 Mo;0 = 2-94 

 Na„0 = 5-78 

 K/J = 2-73 

 P2O5 = 0-85 

 igu. = 0-23 



!)'J-45 



