Report on the Rock-Specimens. 325 



Of the more finely-grained halleflinta-like felsites, one specimen 

 without phenocrysts is seen under the microscope to consist of 

 minute rectangular felspars and interstitial quartz, with shreds of 

 the same micaceous or chloritic mineral as in the preceding rock. 



Another specimen has a somewhat similar base, but contains 

 phenocrysts of rounded and corroded quartz, orthoclase, oligoclase and 

 muscovite : occasionally the quartz and felspars are aggregated together 

 in patches looking like inclusions of granite : one orthoclase pheno- 

 cryst has a remarkable micropegmatic intergrowth of quartz. 



A third honey-yellow hornstone-like specimen shows the same 

 phenocrysts, only smaller and in less amount, in a dense microfelsitic 

 base showing in parts imperfect spherulitic structure. 



SLATES AND QUARTZ-GRITS. 



These rocks are of interest as being apparently the only sedi- 

 mentary rocks found in situ in Victoria Land. 



The pale-green slate, of which a very large number of specimens 

 were collected, constitutes the main mass of Duke of York Island. 

 It also occurs together with quartz-grits on the neighbouring main- 

 land (Geikie Land), and the same formation extends along the coast 

 towards Cape North. According to Mr. Bernacchi, pieces of slate 

 were also seen at the foot of Mount Melbourne in Newnes Land. 



The slate of Duke of York Island is in parts traversed by veins 

 of quartz, near the contact of which with the slate much vermicular 

 chlorite has been developed. Some of the specimens of slate are 

 much contorted into sharp folds in which the quartz veins are 

 involved, showing that the latter were formed prior to the folding of 

 the slate. Iron pyrites in sharply-defined cubic crystals is dissemi- 

 nated in patches abundantly through these rocks. 



A careful examination of the numerous specimens of the slate 

 has unfortunately not led to the discovery of any fossil remains. 



Under the microscope the slate is seen to consist of a colourless 

 muscovite-like mica, shreds of green pleochroic chlorite which gives 

 the colour to the rock, and small quartz grains. It varies in texture 

 from a very fine-grained rock in which quartz grains are scarcely 

 apparent, to one approaching a quartz-grit in which quartz grains 

 seem to be the main constituent. 



The quartz-grits are of the same pale green colour as the slates, 

 but are more coarsely-grained and show no slaty cleavage. A boulder 



