32 



HARDWICKE'S SCIENG E-GOS 8 IP. 



indicate different species. Mr. Murray believes, 

 however, that only one form is met with on one 

 sphere ; and that in order to produce the numerous 

 forms figured by Hseckel and Oscar Schmidt, all of 

 which, and many additonal varieties, he has observed, 

 the spheres must vary in age and development, or 

 i n kind. Their constant presence in the surface-net, 

 in surface-water drawn in a bucket, and in the 

 stomachs of surface animals, sufficiently proves that, 

 like the ooze-forming foraminifera, the coccoliths 

 and rhabdoliths, which enter so largely into the 

 composition of the recent deep-sea calcareous for- 

 mations, live on the surface and at intermediate 

 depths, and sink to the bottom after death. Cocco- 

 spheres and rhabdospheres have a very wide but not 

 an unlimited distribution. From the Cape of Good 

 Hope they rapidly decreased in number on the sur- 

 face, and at the bottom as we progressed south- 

 wards. The proportion of their remains in the 

 Globigerina ooze near the Crozets and Prince 

 Edward Island was comparatively small ; and to 

 this circumstance the extreme clearness and the 

 unusual appearance of being composed of Globi- 

 gerinse alone was probably mainly due. We found 

 the same kind of ooze nearly free from coccoliths 

 and rhabdoliths in what may be considered about a 

 corresponding latitude in the north, to the west of 

 Faroe. Before leaving the subject of the modern 

 chalk, it may be convenient to pass on to stations 

 158, 159, and 160, on March 7th, 10th, and 13th, 

 on our return voyage from the ice. The first two of 

 these, at depths of 1,800 and 2,150 fathoms re- 

 spectively, are marked on the chart " Globigerina 

 ooze " ; and it will be observed that these soundings 

 nearly correspond in latitude with the like belt 

 which we crossed going southwards ; the third 

 sounding at a depth of 2,600 fathoms is marked 

 "red clay." 



According to our present experience, the deposit 

 of Globigerina ooze is limited to water of a certain 

 depth, the extreme limit of the pure characteristic 

 formation being placed at a depth of somewhere 

 about 2,250 fathoms. Crossing from these shal- 

 lower regions occupied by the ooze into deeper 

 soundings, we find universally that the calcareous 

 formation gradually passes into and is finally 

 replaced by an extremely fine pure clay, which occu- 

 pies, speaking generally, all depths below 2,500 

 fathoms, and consists almost entirely of a silicate 

 of the red oxide of iron and alumina. The transi- 

 tion is very slow, and extends over several hundred 

 fathoms of increasing depth ; the shells gradually 

 lose their sharpness of outline and assume a kind 

 of " rotten " look and a brownish colour, and become 

 more and more mixed with a fine amorphous red- 

 brown powder, which increases steadily in propor- 

 tion until the lime has almost entirely disappeared. 

 This brown matter is in the finest possible state of 

 subdivision, so fine that when, after sifting it to sepa- 



rate any organisms it might contain, we put it into 

 jars to settle, it remained for days in suspension, 

 giving the water very much the appearance and 

 colour of chocolate. In indicating the nature of 

 the bottom on the charts, we came, from experience 

 and without any theoretical consideration, to use 

 three terms for soundings in deep water. Two of 

 these, Gl. oz. and r. cl., where very definite, and 

 indicated strongly-marked formations, with appa- 

 rently but few characters in common ; but we fre- 

 quently got soundings which we could not exactly 

 call either " Globigerina ooze " or " red clay " ; and 

 before we were fully aware of the nature of these 

 we were in the habit of indicating them as " grey 

 ooze" (gr. oz.). We/ now recognize the "grey 

 ooze " as an intermediate stage between the Globi- 

 gerina ooze and the red clay ; we find that on one 

 side, as it were, of an ideal line, the red clay 

 contains more and more of the material of the 

 calcareous ooze, while on the other the ooze is mixed 

 with an increasing proportion of " red clay." 



Although we have met with the same phenomenon 

 so f recmently that we were at length able to predict 

 the nature of the bottom from the depth of the 

 sounds with absolute certainty for the Atlantic and 

 the Southern Sea, we had perhaps the best oppor- 

 tunity of observing it in our first section across the 

 Atlantic, between Teneriffe and St. Thomas. The 

 first four stations on this section, at depths from 

 1,525 to 2,220 fathoms, show Globigerina ooze. From 

 the last of these, wliich is about 300 miles from 

 Teneriffe, the depth gradually increases to 2,710 

 fathoms at 500, and 2,950 fathoms at 750 miles from 

 Teneriffe. The bottom in these two soundings 

 might have been called " grey ooze " ; for although 

 its nature has altered entirely from the Globigerina 

 ooze, the red clay into which it is rapidly passing 

 still contains a considerable admixture of carbonate 

 of lime. 



The depth goes on increasing to a distance of 

 1,150 miles from Teneriffe, when it reaches 3,150 

 fathoms ; there the clay is pure and smooth, and 

 contains scarcely a trace of lime. From this great 

 depth the bottom gradually rises, and with decreas- 

 ing depth the grey colour and the calcareous 

 composition of the ooze return. Three sound- 

 ings in 2,050, 1,900, and 1,950 fathoms on 

 the "Dolphin Pise," gave highly characteristic 

 examples of the Globigerina formation. Passing 

 from the middle plateau of the Atlantic into the 

 western trough, with depths a little over 3,000 

 fathoms, the red clay returned in all its purity ; and 

 our last sounding in 1,120 fathoms before reaching 

 Sombrero, restored the Globigerina ooze with its 

 peculiar associated fauna. This section shows also 

 the wide extension and the vast geological importance 

 of the red clay formation. The total distance from 

 Teneriffe to Sombrero is about 2,700 miles. Pro- 

 ceeding from east to west, we have about 80 miles 



