y =99-94 



322 PROF. HARRISON AND MR. JUKES-BROWNE ON [Aug. 1 895, 



have isolated from the Pacific deposit, and in the same proportions, 

 namely about one third of the former to two thirds of the latter, 

 the composition of the resulting compound would approach very 

 nearly that of the Tertiary deep-sea clays, differing ouly in having 

 larger amounts of iron and lime. Such difference would of course 

 soon be removed by the action of percolating water. As the point 

 is of some interest, we append the calculated composition of such a 

 mixture : — 



Water „ 7"13"| 



Colloid silica 445 



Combined silica 46-95 



Alumina 19 - 22 



Iron oxides 12-91 



Manganese peroxide 1'53 



Lime 3 - 06 I 



Magnesia 1*20 



Potash 1-25 I 



Soda 253; 



IV. The Calcareous Oozes. 



In dealing with the three samples of calcareous oozes with which 

 Dr. John Murray kindly supplied us, the same methods were 

 employed as in the case of the Red Clay. As might be expected, 

 the greater portion of each sample consists of calcium carbonate, the 

 quantity of organic silica is generally small, and that of quartz much 

 smaller ; there is always a certain amount of argillaceous or earthy 

 matter, and a variable proportion of adherent sea-salts. 



As both the calcium carbonate and the colloid silica may be re- 

 garded as derived from organisms, the results of the analyses may 

 be arranged under three heads : — (1) Organic constituents, (2) 

 Argillaceous and earthy matter, (3) Adherent sea-salts. 



The first sample (A) was from a 'Challenger' dredging in the Pacific, 

 Station 224, lat. 7° 45' N., long. 144° 20' E., depth 1850 fathoms. 



The second sample (B) was also from a ' Challenger ' dredging, in 

 the South Atlantic, Station 338, lat. 21° 15' S., long. 14° 2' W., 

 depth 1990 fathoms. 



The third (C) was obtained by the ' Buccaneer' in 1886, from a 

 dredging in the South Atlantic, lat. 0° 1' S., long. 15° 56' 5" W., 

 depth 1845 fathoms. 



Each was dried at a temperature of from 230° to 240° Fahr. 

 before analysis, and it should be mentioned that we had asked 

 Dr. Murray to furnish us with samples of the more highly calcareous 

 oozes, such as might be comparable with Tertiary and Cretaceous 

 chalks. This accounts for their all containing a very high propor- 

 tion of carbonate of lime. 



The following are the analyses of these samples : — 



Organic Constituents. A. P». C. 



Organic matter and combined water . 182 1-78 "86 



Calcium carbonate 79 79 91-17 89-50 



Calcium phosphate - 24 -31 -11 



Colloid silica 3-87 -77 1-61 



