332 SoittJierii Cross. 



volcanic rocks, as already pointed out, the phonolitic trachytes present 

 striking analogies with the phonolitic rocks of New Zealand. 



As far as it is possible to judge from the present collection, the 

 geology of Victoria Land in its threefold character (Archtean and 

 PalfBozoic rocks, long uneventful period of terrestrial conditions, 

 followed by recent volcanic eruptions) is similar to that of East 

 Africa and Southern India. Too much stress, however, must not 

 be laid on this apparent similarity, since so little is known of the 

 interior, the future exploration of which may possibly lead to the 

 discovery of fossiliferous Mesozoic rocks which may help to bridge 

 over the long interval between the Palaeozoic slates and the recent 

 basalts. 



EXPLANATION OF PLATE LIII. 



Microscope-sections of Antarctic Rocks. 



Fig. 1. — Plagioclase-olivine-augite-biotite rock. 



Finely-striated plagioclase felspars with patches of olivine (laigo irregular 



crystal near the centre and smaller fragments), pale green augite (small 



fragments showing cleavage), and biotite. 

 Magnification, 10 diam., 2-iu. objective. 

 Fig. 2. — Biotite-hornblende-granite with allanite. 



Two crystals of allanite are seen at the top, and a smaller rounded fragment 



below on the right. 

 Magnification, 10 diam., 2- in. objective. 

 Fig. o. — Kenyte-iike rock. 



At the top on the right is a crystal of anorthoclase showing the fine twin- 



striatious as seen between crossed nicols; immediately below is a rounded 



fragment of red altered olivine; the other two phenocrjsts are of augite with 



magnetite inclusions. 

 Magnification, 18 diam., 1-in. objective. 

 Fig. 4. — Phonolitic trachyte. 



At the top on the left is a rounded crystal of yellow olivine with au inclusitm 



of apatite and a border of a^girine-augite ; below is a iihenocryst ofanorihu- 



clase ; the dark shreds and patches in the grouudmass consist of £egirine- 



augite. 

 Magnification, 18 diam., 1-in. objective. 

 Fig. 5. — Horn blei. de-basalt. 



The section shows small phenocrysts of basaltic-hornblende suriounded by a 



zone of magnetite, felspar laths, and rhombic sections of olivine in a glassy 



base. 

 Magnification, 18 diam., 1-in. objective. 

 Fig. (). — Tuft" with fragments of perlitic kenyte and basalt. 



Me>st of the section is occupied by a fragment of kenyte showing perlitic 



structure; on the light is a fragment of glassy basalt. 

 Magnification, o5 diam., J-in. objective. 



