OOZES 219 



metallic nuclei, have been met with, and have also been 

 extracted from the manganese nodules after these have 

 been broken up in a mortar ; these spherules are sup- 

 posed to have fallen from interstellar space, and are 

 hence called " cosmic spherules." In some positions, 

 again, there are small zeolitic crystals (phillipsite), as 

 individuals, twins, stellate groups, and spherulitic 

 aggregations ; these are supposed to be secondary pro- 

 ducts, formed " in situ," arising from the decomposition 

 of the basic volcanic particles present in the deposits. 



Red Clay is estimated to cover an area of about 

 51,500,000 square miles (or 133,975,000 square kilo- 

 metres) — i.e., about 40,800,000 square miles in the 

 Pacific Ocean, about 5,800,000 square miles in the 

 Atlantic Ocean, and about 4,900,000 square miles in the 

 Indian Ocean. 



2. Radiolarian Ooze. — This deposit is distinguished 

 by the abundance of the skeletons of Radiolaria, and 

 is found typically in very deep water in the tropical 

 regions of the Pacific and Indian Oceans. It is 

 otherwise similar to the Red Clay just described, and 

 may contain a few shells of pelagic Foraminifera and 

 small angular volcanic mineral particles, fragments 

 of pumice, augite, felspars, hornblende, magnetite, 

 volcanic glass, frequently altered into palagonite, as 

 well as manganese nodules, sharks' teeth, and ear- 

 bones of cetaceans. 



Radiolarian Ooze is estimated to cover an area of 

 about 2,290,000 square miles (or 5,957,000 square 

 kilometres) — i.e., about 1,160,000 square miles in the 

 Pacific Ocean, and about 1,130,000 square miles in the 

 Indian Ocean. 



3. Diatom Ooze. — This deposit is distinguished by 

 the prominence of Diatom frustuks (skeletons), and is 

 therefore characteristic of those regions in which 



