IN THE WAKE OF THE “ CHALLENGER. 
27 
share in forming the floor of the ocean, there seems to be no 
doubt, according to Professor Wyville Thomson, that it “is 
essentially the insoluble residue, the ash, as it were, of the 
calcareous organisms which form the Globigerina ooze ; ” after 
the carbonate of lime, which forms about 98 per cent, of this 
ooze, has been by some means removed. A sample of such 
ooze was washed by Mr. Buchanan, and subjected to the action 
of a very dilute acid, and he found that there remained, after 
the carbonate of lime had been removed, about one per cent, 
of a reddish mud, consisting of silica, alumina, and red oxide 
of iron. Now, as all sea-water contains a certain proportion 
of free carbonic acid, which is greatest at the greatest depths,* 
it is very probable that this is the agent by which the solution 
of calcareous matter has been brought about. It is evident, 
then, that clay , which has hitherto been regarded as essentially 
the product of the disintegration of older rocks, may, under 
certain circumstances, be an organic formation, like chalk.f 
Professor Wyville Thomson, having formerly held the contrary, 
has been at length led to believe, from the results of Mr. 
Murray’s explorations of the surface and sub-surface water, that 
the Globigerince pass their whole lives in the superjacent water, 
only subsiding to the bottom when they are dead. Dr. Car- 
penter believes that “ the truth lies between two extreme 
views,” and that the animals sink to the bottom whilst yet 
living , in consequence of the increasing thickness of their 
shells, and not only continue to live on the sea-bed, but also to 
multiply there.J 
Mr. Buchanan made some observations on sea-water ice, 
which is known, when melted, to be unfit to drink. Fragments 
of pack-ice, and also of some ice which had formed in a bucket 
of sea-water on board, were submitted to various tests, and it 
was found that the salt is not contained in it only in the form 
of mechanically enclosed brine, but exists in the solid form, 
either as a single crystalline substance or as a mixture of ice 
and salt-crystals. The sea-water ice which had crystallised in 
hexagonal planes, as common salt does when separating from 
solutions at temperatures below 0° C., may possibly have some 
analogy to the isomorphous mixture occurring amongst 
minerals. § 
* There is, moreover, according to Mr. Sorby, an increase of solvent power 
for carbonate of lime possessed by water under greatly augmented pressure. 
t See Preliminary Notes on the Nature of the Sea Bottom procured by the 
Soundings of H.M.S. Challenger , during her Cruise in the Southern Sea , in 
the early part of the year 1874. — “Proc. Royal Soc.” vol. xxiii. pp. 44, 
et seq. 
f Remarks on the preceding paper. — Ibid. p. 234. 
§ Some Observations on Sea-Water Ice. “Proc. Royal Soc.” vol. xxii. 
p. 431. 
