190 



MR. JTJKES-UEOWIfE AND PEOF. HARRISON 



rently exhibit a closer resemblance in composition to certain of the 

 l^arbados radiolarian deposits than to the argillaceous earths.^ All 

 the ' Challenger ' samples contained calcium carbonate, many of 

 them in considerable quantity, the range being from '92 to 22-63 

 per cent.^ 



Several of the samples (Nos. 8, 10, 15, 16, 17, and 22) contained 

 less than 3 °/^ of calcium carbonate, and such samples would, upon 

 exposure to the action of percolating water during lengthened 

 jDcriods, assume compositions similar to those of the Barbados 

 argillaceous earths. Apparently also the amounts of calcium and 

 magnesium carbonates assumed to be present in the ' Challenger ' 

 samples analysed by the late Dr, Erazier were determined by con- 

 sidering that all the lime and magnesia dissolved from the clays by 

 hydrochloric acid in quantities above those necessary to combine 

 with the sulphuric and phosphoric acids, were in the form of carbo- 

 nates, and not, as in all probability they must have been, in part as 

 silicates decomposable by acids. 



In order to facilitate comparison, we have rearranged as follows 

 the analyses of these samples so as to render them more easily 

 comparable with those of the Barbados rocks: — 



Number of sample 



Station 



8 



19 



3000 



10 



21 

 3025 



15 



252 

 2740 



16 

 253 

 3125 



17 



256 

 2950 



22 

 281 

 2385 







Combined water, &c 



Colloid sihea 



7-44 



27-68 

 25-16 



10-33 



1-57 

 12-91 



7-81 



1-49 



•96 



trace 



3-10 



1;03 



-52 



5-92 

 24-70 

 30-20 



12-25 



6-73 

 7-04 



5-51 



2-44 



-51 



trace 



3-48 



•81 



•41 



3-60 

 21-89 

 37-70 



13-14 



2-60 

 5-23 



7-85 



trace 



2-22 



-51 



-41 

 1-50 



•35 



4-50 

 24-70 

 37-40 



7-95 



3-88 

 8-31 



7-75 

 •55 

 •92 

 •37 

 •19 



2-70 

 ■28 



•50 



4-50 



24-95 

 34-82 



9-77 



2-00 

 6-00 



11-37 



■6S 



1-69 



-42 



-48 



1-33 



1-14 



-85 



100-00 



7-70 

 32-60 

 11-27 



24-60 



3-80 



8-80 



1-60 



2-73 



2-50 



trace 



si. trace 



3-24 



•84 



•32 



Combined silica and quartz 

 Iron peroxide soluble in 

 HOI 



Iron peroxide not soluble in 

 HCl 



Alumina soluble in HCl ... 

 Alumina not soluble in 

 HCl 



Manganese peroxide 



Calcium carbonate 



Calcium sulphate 



Calcium phosphate 



Magnesium carbonate 



Lime not soluble in HOI . . . 



Magnesia not soluble in 



HOI 





100-00 



100-00 



100-00 



100-00 



100-00 



^ Haeckel remiarks that Stations 241 to 245, -which are classed in the Station 

 Eeport as being red clays, ' might have been almost as appropriately termed 

 radiolarian ooze.' ' Challenger ' Eeports, vol. xviii. pt. i. Eadiolaria, p. cxlix. 



^ Samples Nos. 1, 2, 12, and 19 in the table above referred to sho-w amounts of 

 calcium carbonate ranging from 36 80 to 60-29 per cent., but we have been 

 informed by Dr. John Murray that these samples consisted of red clays after the 

 finer portions (i. e. the clay) had been washed away. It appears to us to be 

 somewhat misleading to include these samples in a table showing the com- 

 position of red clay, without a footnote pointing out their exceptional character. 



