276 THE VOYAGE OF H.M.S. CHALLENGER. 



No observations for current could be obtained, except in the ordinary way, viz., by 

 difference between the dead reckoning and observed position of the ship. 



On the 20th October, at Station 136, the velocity of the wind was on an average 14 

 miles per hour. 



Between the Tristan plateau and the south of Africa, there is a wide and deep 

 depression, where depths of 2550 and 2650 fathoms were obtained. The deposits at 

 these depths contained 35 and 26 per cent, of carbonate of lime, consisting of pelagic 

 Foraminifera and their broken parts. The mineral particles were rather abundant, 

 making up 50 per cent, of the whole deposit at the greater depth, and consisted of 

 rounded and angular fragments of quartz, orthoclase, hornblende, tourmaline, and augite. 

 These mineral fragments, some of which were fully one millimetre in diameter, indicate 

 that these soundings are within the area which is occasionally affected with Antarctic 

 ice. The two soundings in 2325 and 1250 fathoms contained 47 and 50 per cent, of 

 carbonate of lime; the mineral particles seldom exceeded 0'07 mm. in diameter, and 

 consisted of quartz, glauconite, felspar, augite, and magnetite. About 5 per cent, of these 

 deposits were made up of Eadiolarians, Diatoms, and Sponge spicules. 



A dredging at 2100 fathoms, near the edge of the Tristan plateau, was unproductive, 

 the bottom appearing to be hard or rocky. A trawling in 2550 fathoms yielded two 

 small Starfish, a bivalve Mollusc, and a few Crustaceans. 



The tow-nets did not yield such a variety of forms as in the sections across the 

 tropical portions of the Atlantic. 



Tlie Holothurioidea. — Dr. Hjalmar Theel, of Upsala, gives the following summary of 

 his Report on the Holothurioidea collected by the Expedition, the first part of which has 

 been published : — 1 



" The Holothurians are very widely distributed in the sea, and representatives of them 

 are found from the shores down to the greatest depths all over the bottom of the ocean. 

 Before the Challenger Expedition set out, our knowledge was limited almost exclusively 

 to such forms as live on, or in the neighbourhood of, the shores ; but from the 

 investigations of the Expedition, not only has our knowledge of the shallow water 

 forms been considerably increased, but the obscurity which involved the abyssal fauna has 

 been greatly dispelled. It seems to be a fact that only a comparatively small number of 

 Holothurians nearly related to the true shallow water forms are met with in the deep 

 sea. The majority of Holothurians dredged from the bottom of the ocean present such 

 important peculiarities, and differ so strikingly from the shallow water forms, that it has 

 been necessary to arrange them in a new order, Elasipoda, equivalent to the orders 

 Apoda and Pedata, already known. This summary is intended to show how far our 

 knowledge of the Holothurians has been increased by the Challenger Expedition, which 



1 Report on the Holothurioidea, — the Elasipoda, by Hjalmar Theel, Zool. Chall. Exp., part xiii., 1881. 



