clvi 



THE VOYAGE OF II. M.S. CHALLENGER. 



from the coast. In general they are characterised by great uniformity, corresponding to 

 the constancy of the conditions under which they are Laid dow-n ; they may be di^dded 

 into three categories, the true Radiolarian ooze (§ 237), Globigerina ooze (§ 238), and red 

 clay (§239). Of these three most important deep-sea formations the first is by far the 

 richest in Radiolaria, although the other two contain often very many siliceous shells. 



The marvellous discoveries of the Challeuger have thrown upon the nature of marine deposits 

 an entirely new light, which justifies most important conclusions regarding the geographical 

 distribution and geological significance of the Eadiolaria, Since Dr. John Murray and the Abb4 

 Eenard will treat fully of these interesting relations in a forthcoming volume of the Challenger 

 series (Eeport on tlie Deep-Sea Deposits), it will be sufficient here to refer to their preliminary 

 publication already published (Narrative of the Cruise of H.M.S. Challenger, 1885, vol. ii. part ii. 

 pp. 915-926); see also the earlier communications by John Murray (1876, L. N. 27, pp. 518-537), 

 and by Sir Wyville Thomson (The Atlantic, L. K 31, vol. i. pp. 206-246). In the Narrative 

 {loc. cit., p. 916) the following table of marine deposits is given : — 



Terrigenous deposits. 



Abysmal deposits. 



Shore formations, 

 Blue mud. 



Green mud and sand. 

 Red mud. 



Volcanic mud and sand. 

 Coral mud and sand. 

 Coralline mud and sand, 



\ Globigerina ooze, 

 I Pteroix)d ooze, 

 -^ Diatom ooze, 

 I Radiolarian ooze, 

 [ Red clay, 



Found in inland seas and along the shores of 

 continents. 



I Found around oceanic islands and alongtlie shores 

 ( of continents. 



Found in the abysmal regions of the ocean basins. 



237. Radiolarian Ooze. — By Radiolarian ooze, in the strict sense of the term, are 

 understood those oceanic deposits, the greater part of which (often more than three- 

 quarters) is composed of the siliceous skeletons of this class. Such pure Radiolarian ooze 

 has only been found in limited areas of the Pacific and Indian Oceans. It is most 

 conspicuous in the Central Pacific, between lat. 12° N. and 8° S., long. 148° W. to 152° W., 

 the depth being everywhere between 2000 and 3000 fathoms (Stations 266 to 268 and 

 272 to 274). In the deepest of the Challenger soundings (Station 225, 4475 fathoms) 

 the bottom is composed of pure Radiolarian ooze, as well as at the next Station in the 

 Western Tropical Pacific (Station 226, 2300 fathoms), the latitude varying from 12° N. to 

 15° N., and the longitude from 142° E. to 144° E. In the Indian Ocean also, pure 

 Radiolarian ooze was found in the year 1859 between Zanzibar and the Seychelles, this 

 being the first known example of it (§ 230). On the other hand, it has not yet been 

 found in the bed of the Atlantic ; but the Tertiary formations of Barbados (Antilles, § 231) 

 like those of the Nicobar Islands (Further India), are to be regarded as pure Radiolarian 



