XI 



The Bed of the Oceans 207 



at all depths ; the small number of foraminifera living in 

 the cold and comparatively fresh surface water accounts for 

 the small quantity of carbonate of lime in the deposits of 

 that region. The whole Southern Ocean is within the limits 

 of icebergs drifting from the Antarctic region, and the Diatom 

 ooze often contains a considerable proportion of terrigenous 

 deposit, the nature of which proves the existence of conti- 

 nental rocks, and thus of an unexplored continent near 

 the south pole. 



277. Red Clay. The deepest parts of every ocean are 

 covered with a stiff clay of a deep brown or red colour, 

 containing little or no carbonate of lime. Red clay is the 

 distinctive deposit of the Abysmal Area, toward the upper 

 margin of which it passes very gradually into Globigerina 

 ooze ; and where radiolarians abound on the surface the 

 accumulation of their spicules gives to it the name of 

 Radiolarian ooze. It covers more than half the area of 

 the Pacific Ocean. Red clay is exactly like the residue 

 of Globigerina ooze after the carbonate of lime has been 

 removed. The snowfall of calcareous shells from the sur- 

 face of the open ocean melts into solution before reaching 

 the abysmal depths, but the horny remnants of those shells, 

 siliceous relics of life, waterlogged pumice-stone, wind-borne 

 dust from deserts and volcanoes, ultimately settle down and 

 accumulate on the bottom. The rate of deposit is incom- 

 parably slower than that at which any of the oozes form. 

 Microscopic examination has revealed as one of the con- 

 stituents of Red clay cosmic dust from meteorites ( 134), 

 which falling uniformly over the Earth's surface is concealed 

 by the rapid changes going on in every other region but the 

 still Abysmal Area. The red colour of the clay is due to 

 the formation of ferric oxide and peroxide of manganese 

 from decomposing volcanic material. These oxides also 

 become deposited upon any hard objects lying on the sea- 

 floor, and form nodules composed of layer above layer 

 and often attaining the size of a large potato, to which their 

 usual shape is very similar. Manganese nodules were 

 dredged up in great numbers by the Challe?iger, and in 

 every case the nucleus on which they had formed was 



