o4G l»i; ^[UltltAV UiS THE DEEP AND SHALLuW-WATEll iMAKINE FAUNA 



soundings were situated towards the Antarctic Circle. Tln-ee other soundings greater than 

 1000 fathoms are recorded to the south of the 60th parallel of south latitude. Ross obtained 

 many soundings in depths ranging from 190 to over 600 fathoms (347 to 1097 metres) 

 to the east of Victoria Land and off the Ice Barrier within the Antarctic Circle. Again, 

 in long. 15° W., within the Antarctic Circle, Eoss paid out 4000 fathoms (7315 metres) 

 of line without reaching bottom, so that there is probably a great depth in this position. 

 Wilkes obtained depths of 800 and 500 fathoms (1463 and 914 metres) oft' Adelie Land. 



With the exception of several deep soundings where no bottom was found, this is all 

 we know about the depths in the Southern and Antarctic Oceans. The indications, on 

 the whole, point to a gradual shoaling of the sea-bed from the 40th parallel southwards 

 towards the shores of the Antarctic Continent, situated at some points close ,to the 

 Antarctic Circle, for instance at AVilkes Land, lu some places, however, the sea-bed 

 rises into somewhat shallow plateaus, as around Kerguelen and other oceanic islands, and 

 in other places sinks to great depths, as in the Ross Deep and Barker Basin.^ 



Marine Dej)osits on the Sea-Jloor. — Nearly all the information we have as to the 

 deposits on the sea-bed near to or within the Antarctic Circle is derived from the 

 observations of the Challenger Expedition, together with a few additions from the Ross 

 and Wilkes Expeditions. At her most southerly soundings and dredgings the Challenger 

 procured a Blue Mud made up chiefly of detrital matter from the Antarctic Continent. 

 Imbedded in these muds were large and small fragments of granites, quartziferous 

 diorites, schistoid diorites, amphibolites, mica schists, grained quartzites, sandstones, 

 compact limestones, and partially decomposed earthy shales. These rock fragments 

 were evidently transported from the Antarctic Continent by the icebergs, and their 

 lithological character leaves no doubt that true continental land, and not a group of 

 volcanic islands, is situated within the Antarctic Circle. These rocks were most 

 abundant in the Challenger's dredgings on the Blue Mud at the most southerly 

 stations, but they were met with in diminished numbers in all the dredgings within 

 the area of the ocean aftected at times by floating ice from the Antarctic Seas." 

 Although we have very few observations as to its geographical extension, still, judging 

 from what occurs oft' other continental shores, we may feel sure that the Blue ]\Iud 

 extends all round the Antarctic Continent to a distance of about 200 miles {:yi2, kilo- 

 metres) seawards. 



To the north of the Blue Mud the sea-floor is occupied by a white or cream-coloured 

 deposit chiefly made up of the silicious frustules of Diatoms, with a large admixture of 

 Radiolarians and Sponge spicules. In some places this Diatom Ooze extends north nearly 

 to the 40th parallel. But about the 50tli parallel it appears to be usually replaced by a 



- See Charts in a Summary nf tlie Scientific Results obtained at the sounding, dredging, and trawlin;,' Stations of 

 H.M.S. Challengoi', 1895. 



- Tliisviewas to tlie origin of these continental rocks is supported l)y tlie facts that D'Urvii.le found a rocky islet 

 off Adelie Laud, to be composed of gneiss and granite, that W^ilkes found, on an iceberg in the same locality, boulders 

 of red sandstone, and that Mr Borchgrevink, who landed at Cape Adair from the whaler "Antarctic" in 1895, 

 brought away fragments of mica-schists and microcline-granite, with rpiartz, felspar, tourmaline, and garnets. 



