Vol. 51.] THE CHEMICAL COMPOSITION OF OCEANIC DEPOSITS. 325 



include sea-salts, organic matter, and other ingredients. Allowing 

 for this, it will be seen that the two estimates agree very closely : — 



Analysis by 

 Harrison & 

 Williams. 



Carbonate of lime 79 - 79 



Siliceous organisms 3'87 



Water and organic matter . 1-82 



Minerals and fine washings 971 



Adherent sea-salts 457 



9976 



Estimate by 



Dr. John 



Murray. 



79-20 



5-00 



15-80 



100 00 



The second sample (B) analysed by us was also analysed in mass 

 by Dr. Brazier, and the results obtained by him are as follows T : — 



Loss on ignition after drying at 230° F 1 *40^| 



f Alumina- "65 



I Ferric oxide '60 



c , , , . Calcium phosphate "90 



Soluble in n , . „ r , i r . . in 



hjdrochlone < 2^^^"^==^= ^[^ 



Magnesium carbonate "87 1 



Manganese oxide nil. | 



Silica 1-36 | 



Insoluble— Alumina, ferric oxide, and silica l'49j 



On comparing this with the analysis of B on p. 323, the mistake 

 made in digesting the material in boiling hydrochloric" acid is shown 

 by the difference in the amounts of insoluble residue and soluble 

 silica. By Dr. Brazier's method only 1-49 of insoluble residue was 

 left, whereas the sample really contains nearly 4 per cent, of 

 silicates, which ought to be reckoned as insoluble matter. Again, 

 1*36 per cent, of silica was rendered soluble by Dr. Brazier's treat- 

 ment, but the amount of soluble colloid silica present is only 077 

 per cent. 



Another point of some importance is that Dr. Brazier reckons all 

 the magnesia as carbonate, and makes the total amount of calcium 

 and magnesium carbonates come to 93*41 per cent. We did not 

 find enough carbonic acid to combine with the magnesia, and con- 

 sider this to be partly in the state of chloride and partly as silicate ; 

 the magnesium chloride and calcium sulphate being part of the 

 adherent or occluded sea-salts. 



On referring to the ' Challenger ' Report (p. 446) we find a sub- 

 sequent note by Element, stating that 1*0185 gram of the ooze dried 

 at 110° C. gave 0*4120 gram of carbonic acid, corresponding to 

 0*9364 gram of carbonate of lime, which is equivalent to 91*94 per 

 cent. This is a close approximation to our own result, 91*17 per 

 cent. 



Of the third sample, obtained by the ' Buccaneer,' no previous 

 analysis has been published. It is seen to be a highly calcareous 

 ooze very similar to the ' Challenger ' sample B from Station 338 , 



1 ' Challenger ' Eeport on Deep-Sea Deposits, p. 444. 



