5 CIENCE-GOSSIP. 



to examine these chemically and physically. To 

 ascertain the temperature of the ocean at various 

 depths from surface to bottom. To catch, examine, 

 and bring home the creatures that live in the surface 

 and deep waters of the ocean and on the bed of the sea 

 itself. To measure ocean currents. To take 

 magnetical and meteorological observations daily. 

 In short, to carry on whatever researches might throw 

 light on the physical, chemical, and biological 

 conditions of the deep sea, and, in addition, to 

 examine the plants, animals, and geological structure 

 of all oceanic islands, and other Httle-frequented lands 

 visited by the ship." 



rf[\^d^ ^]\ 





Radiolaria. 



The "Challenger" left Sheerness in December, 

 1872, and arrived home in May, 1876, after passing 

 round the world by an indirect and sinuous route. 

 The voyage covered some 69,000 miles of ocean, in 

 which over 400 deep-sea soundings were taken. One 

 of the most important results of its investigations has 

 been to demonstrate that the bottom of our modern 

 ocean, far from being the abode of death, is peopled 

 by many extraordinary forms of life. Also that where 

 the depth can be measured by miles, we have a 

 teeming population of the humbler forms. All the 

 great types among the invertebrata have been found 

 at depths beyond three miles. These include 

 echinoderms (sea-urchins, brittle-stars, sea-cucumbers), 

 brachiopods, annelids, sea-spiders, barnacles, shrimps, 

 and a few corals ; whilst amongst the vertebrata, fishes 

 have been dredged of curious and interesting forms. 

 These were found, both in the living state and also in 

 a skeletonised condition, where they possessed a hard 

 skeleton. The most interesting portion to geologists 

 of the discoveries was undoubtedly the satisfactory 

 determination of the nature of the deposits forming on 

 the ocean's bed, and which in many cases formed the 

 imbedding matrix for the remains of the higher 

 forms of creatures just mentioned. These deposits, 

 "oozes," as they are called, were found, by both 



chemical and microscopical examination, to bear 

 a close resemblance to those substances which are 

 familiarly known to us as Chalk. Indeed, a promi- 

 nent member of the "Challenger" expedition 

 announced, whilst the novel results found were 

 scarcely thoroughly examined, that we were still 

 living in the cretaceous epoch. This statement is, 

 however, now completely scouted by scientific men ; 

 but it was peifectly excusable in the early excitement 

 aroused. Deposits were found, some consisting 

 principally of microscopic calcareous (chalky) for- 

 aminifera or pteropoda, others principally composed 

 of silicious (flinty) microscopic organisms belonging to 

 the order Radiolaria, or to the vegetable Diatomaceae. 

 These oozes are pelagic, that is, occur far from land. 



It is estimated that for about 200 miles out at 

 sea, all around our continental coasts, the bottom 

 of the sea is covered by what have been classed as 

 Shore Deposits. These result from the gradual 

 denudation of the land, and consist of great accumu- 

 lations of river and coast detritus. The clay or mud 

 brought down by rivers is carried far out to sea in 



Sponge Spicl'les. 



a state of fine sub-division. It is deposited beyond 

 the influence of tides and currents. Sand similarly 

 carried down by the rivers to the sea, in a state of 

 suspension, isby reason of its heavier nature, deposited 

 within this 200-niile limit earlier than the clay, so that 

 in this area we have sedimentary rocks forming. 

 These will constitute the clays, the chalks, and the 

 sands as true geological formations in ages to come. 



Beyond this limit, we arrive at a point out of reach of 

 the influences of rivers and tides, and difti^rent condi- 

 tions prevail. Roughly speaking, after we pass beyond 

 this imaginary boundary, and reach those parts where 

 the depth of the ocean varies from one to two and 

 half miles, we come, both in temperate and tropical 

 regions, to those areas whece the great calcareous 



