408 



THE VOYAGE OF H.M.S. CHALLENGER. 



other Foraminifera; Coccospheres and Rhabdoliths; fragments of Pteropods, and other 

 pelagic Molluscs ; Ostracode valves, fragments of Echinoderms, Polyzoa, and other 

 calcareous organisms. The mineral particles in these green muds were about - 2 mm. 

 in diameter, and consisted of rounded fragments of quartz, felspars, hornblende, magnetite, 

 mica, volcanic glass, in addition to glauconite. There were a few Radiolarians and 

 Sponge spicules. A quantity of the glauconitic grains and casts were carefully collected, 

 after the removal of the calcareous organisms by dilute acid, and a careful analysis of these 

 was made by Dr. Sipocz. A microscopic examination of the substance analysed showed 

 it to be, by estimation, made up of about 1 per cent, of white, pale grey, and yellow 

 casts, about 25 per cent, of pale green casts, about 60 per cent, of dark green ones, and 

 about 5 per cent, of mineral particles and siliceous organisms. In practice it was found 

 impossible to separate the siliceous organisms and small mineral particles from the casts. 



A nalyses of Glauconitic Grains and Casts. 



I. 0*7312 gramme of the substance fused with double carbonate .of soda and potash 

 gave 0-0416 grm. water (H 2 0), 0'3788 grm. silica (Si0 2 ), 0'1896 grm. ferric oxide 

 (Fe 2 0„), 0'0634 grm. alumina (A1 2 3 ), traces of manganese, 0"0093 grm. lime (CaO), and 

 0"0618 grm. magnesium pyrophosphate (Mg 2 P 2 7 ), equivalent to 0'02227 grm. magnesia 

 (MgO). 



