XVI.] FORAMINIFERAL LAND. 269 



But there are some areas of these oceans, occupying many 

 thousand square miles, in which the sea-bottom is covered, 

 not with Globigerina-ooze, but with a red mud, which 

 appears to be nothing but clay in a very finely divided 

 state. These areas are usually met with only at a very 

 great depth, over 2,500 fathoms in fact; and the naturalists 

 of the Challenger observed that, in passing from the adjacent 

 region covered with the ordinary Globigerina-ooze, into one 

 of these red-clay areas, a region, covered with a sort of grey 

 mud (" grey ooze "), intermediate in its character between 

 the Globigerina-ooze and the red clay, was traversed. Where 

 the grey ooze began, the Globigerina shells appeared to be 

 corroded, as if they had been attacked by an acid ; and, as 

 the red clay was approached, they became more and more 

 fragmentary, and at length altogether disappeared. 



There can be no doubt that the foraminiferal shower 

 falls over the area, occupied by the grey ooze and the red 

 clay, just as persistently as elsewhere. What then becomes 

 of the shells ? There seems to be no escape from the 

 conclusion that the calcareous matter of which they are 

 composed is dissolved away. The Globigerina are so 

 minute, that their skeletons must take a great length of time 

 to subside through the three or four miles of water, which 

 overlie the deeper sea-bottoms. But sea-water contains 

 much carbonic acid; and, it has already been seen, that 

 carbonate of lime, especially if finely divided, is soluble in 

 such water. Hence, it is highly probable, that the fora- 

 miniferal shower is, in part, redissolved before it reaches the 

 bottom ; and that, other things being equal, the greater the 

 depth, the greater will be the loss suffered in this manner. 



The difficulty is to understand, not why the Globigerinm 

 should disappear from the bottom of the very deep parts of 

 the ocean, but why the process of solution should be so 



