682 DR J. H. HARVEY PIRIE ON DEEP-SEA DEPOSITS 



rock fragments and coarse mineral particles with fine-grained particles is typical of the 

 glacial deposits. We had not on the Scotia, unfortunately, an opportunity of making 

 a haul with the dredge in the shallow water off the ice-barrier at Coats Land ; a direct 

 examination of the material accumulating at the face of the barrier would be of the 

 greatest interest. 



A considerable variety of rocks occurs amongst these larger specimens ; but by far 

 the most common are metamorphic gneissic and schistose rocks, granulites, quartzites 

 amphibolites, portions of acid and basic veins of banded gneiss, coarse granitoid forms, 

 garnetiferous gneiss, mica and chlorite schists, cleaved phyllitic slate and hornfels. 

 Igneous plutonic rocks, fairly abundant, are represented chiefly by granites, a few 

 pieces of gabbro and diorite ; volcanic rocks, not very abundant, chiefly by basalts, also 

 by pumice, some pieces of tuff, trachyte, andesite, rhyolite, quartz dolerite, and — of great 

 interest in conjunction with the Cambrian fossils — a characteristic spilitic basalt. Of 

 sedimentary rocks there occur several varieties of sandstone, shale, slate, greywacke, a 

 clay concretion from limestone, and pieces of limestone one of which is of particular 

 interest, containing several species of that peculiar fossil form Arcliaeocyathina. 

 This find, although not in situ, points to the probable occurrence of Cambrian rocks on 

 this side of the Antarctic similar to those in which these fossils were found on the 

 Shackleton Expedition in Victoria Land. The general facies of the rock fragments, 

 however, presuming that they come from the land to the south of the Weddell Sea, 

 indicates the presence there chiefly of metamorphic rocks allied in character to those 

 occurring on the western side of Graham Land (9) and to the gneisses of S. Victoria 

 Land (10). 



(2) Smaller Mineral Particles. — The smaller mineral particles obtained from the 

 ordinary samples of deposit as brought up by the sounding-tube and including every- 

 thing down to 0"05 mm. in diameter, and a certain amount of even smaller fragments 

 (down to about 0'02 mm.), constitute on an average 16'7 per cent, of the deposit, the 

 figure in the great majority being between 10 and 20 per cent. In one sample of 

 pure glacial deposit (No. 21), whose peculiar sandy character is referred to in describ- 

 ing the physical characters of those deposits, the percentage rises to 70, whilst in six 

 it falls to 5 per cent, or less. All these six lie in the portion of the Weddell Sea 

 furthest from land, within the area I described in my preliminary report as Blue mud 

 approximating in some respects to Red clay. The mean diameter of the mineral 

 particles in the various samples works out on an average at 0"09 mm,, the means 

 varying between 0'05 and 0'25 mm. Although the sample (No. 32) with the smallest 

 percentage of mineral particles is also the one with the lowest mean diameter of the 

 particles, it cannot be said that all over there is very much difference in the average 

 size of the smaller mineral particles, between the samples comparatively close to land 

 and those far from it ; there is certainly not the same marked contrast as there is in 

 the amounts of the mineral particles. 



Some of the mineral particles are well rounded, particularly the larger ones, and on 



