their Relation to Geological Funnativns. 201 



gradations apparently consequent on occupying intermediate 

 depths, and often represented by the grey ooze. It would 

 also appear that at the greatest ascertained depths conditions 

 prevail unfavourable to the existence of organisms with calci- 

 ierous tissues or calcareous skeletons. Life, however, still 

 exists in the abyssal basins where the grey and red clays are 

 formed. In several hauls, in one instance from 2975 fathoms, 

 there were brought up : — holothurids of considerable size with 

 rudimentary calcareous neck-rings ; delicate branching, almost 

 membranous Bryozoa ; tube-building annelids, and tests of 

 Foraminifera, the two latter being made up of particles of the 

 red clay alone. And on one occasion, between Kerguelen Island 

 and Melbourne, the " red clay," at the depth of 2600 fathoms, 

 yielded Holothurias, starfishes, Actinias, Palliobranchs, Euplec- 

 tella-siponges, &c. : those with calcareous parts were rather 

 stunted. 



Considering the existence in the ocean of vast numbers o 

 diatoms, polycystines (these, there is no doubt, habitually live 

 at or near the surface), sponges, and other organisms, whose 

 skeletons consist of silica — also that rock-particles in the 

 finest state of division, from their occurrence everywhere in 

 the atmosphere, must be scattered over the sea-bottom by 

 the distributive action of currents, it was to be expected that 

 the foraminifer-ooze would not be purely calcareous. The 

 analyses published by Messrs. David Forbes and Jolm Hunter 

 (late of the Queen's College, Belfast) show that such is actually 

 the fact — the former having found, in a specimen from the 

 depth of 2435 fathoms, 23"34 silica, 5*91 ferric oxide, 5*35 

 alumina* ; the latter, in a specimen taken in 1443 fathoms, 

 26'77 fine insoluble gritty sand (rock-debris), 1*33 alumina 

 (soluble in acids), and 2"17 sesquioxide of iron (soluble in 

 acids) t- Mr. Buchanan, of the ' Challenger',' has found 1 per 

 cent, of a reddish mud, consisting of silica, alumina, and red 

 oxide of iron, after washing and subjecting samples of the ooze 

 to the action of weak acid. These results seem to have satis- 

 fied the scientific Director of the Survey that, allowing certain 

 difficulties as mere matters of detail, the question as to the 

 origin of the red clay is in the main solved. Grant sufficient 

 free carbonic acid in the water of deep ocean-basins to dissolve 

 all calcareous bodies, such as foraminifer-shells, that fall into 

 them, the insoluble constituent alone will remain as a deposit. 

 Professor W. C. Williamson proposed a similar hypothesis 

 many years ago to account for the absence of calcareous shells 

 in the siliceous (Diatomaceous) deposits of Bermuda and Vir- 



* Proc. Royal Soc. vol. xviii. p. 490. t 2b. p. 428. 



