on board H.M.S. 'Challenger? 525 



Globigerina-oom overlying the red clay, or we might suppose that 

 chemical changes are going on in the deeper layers which remove the 

 carbonate of lime. In the second case we may account for a red clay 

 overlying a deposit with many Olobigerince in it by supposing a depression 

 of the bottom after the latter had been laid down ; or we may believe 

 that agencies are now removing carbonate of lime from the surface-layer, 

 and that these were not active in some past time. 



This deposit occurs, in one sounding, in the Pacific at a depth of 2925 

 fathoms in mid-ocean. In the eastern part of the Atlantic it occurs 

 also at great depths. 



The following is a list of the depths at which we have found a 

 Globigerina-ooze : — 







Atlantic 



Ocean. 







fms. 



fms. 



fms. 



fms. 



fms. 



fms. 



1090 



1900 



2200 



1350 



1425 



2275 



1525 



1950 



1675 



900 



1650 



2475 



2250 



2325 



1675 



2025 



2300 



2200 



2225 



1420 



1240 



2660 



2300 



2150 



1945 



2575 



1000 



2675 



2400 



2275 



1975 



2450 



2500 



2400 



2400 



2050 



1150 



2475 



2275 



1500 



2075 



1900 



2300 



2175 



1850 



1900 



780 



2025 



2025 





Southern 



, Ocean. 







fms. 



fms. 



fms. 



fms. 



fms. 



fms. 



1900 



1570 



1375 



Pacific 



1600 

 Ocean. 



1800 



2150 



fms. 



fms. 



fms. 



fms. 



fms. 



fms. 



1974 



1350 



1675 



2925 



1915 



1500 



1100 



1450 



2000 



2425 



1600 



1825 



275 



1700 



1100 



1940 



2025 



1775 



400 



1400 



1850 



2075 







3. Radiolarian Ooze. — Organisms with the siliceous skeletons abound 

 in the surface-waters, and apparently also in the deepest waters, of all 

 the oceans and seas we have visited *. The skeletons of these organisms 

 are found in all, or almost all, the sea-bottoms. Even in those cases 

 where at first sight they would seem to be quite absent, a more careful 

 examination (by dissolving away a large quantity of carbonate of lime 

 where this exists, and examining the sediment by careful washing in the 

 case of clays, &c.) will usually reveal a Eadiolarian skeleton, a Diatom 

 frustule, or broken portions of these. 



It is, however, only in some limited areas that these exuvise rise into 

 such prominence as to be characteristic of the deposit taking place. 

 Such is the case in the Antarctic, where we have a Diatom-ooze, and in 

 the Western and Middle Pacific, where we have the above deposit. 



* They are, however, much more numerous in the Pacific than in the Atlantic 

 especially in the equatorial waters. 



