of Edinburgh, Session 1881 - 82 . 667 
The trawl was used with a swab at one end and a tow-net at the 
other end of the beam, and a bag at the bottom of the netting. In 
the tow-net there was about a litre of mud, and about 5 litres 
in the bag of the trawl. In the trawl there were, besides many 
hundreds of pycnogonids, many fish, some starfish, ophiuroids, 
echini, &c. 
Blue mud with greenish tinge, grey when dry, sandy, calca- 
reous. 
Carbonate of calcium 12 ‘75 per cent., consists of many Cocco- 
liths and Coccospheres, Globigerinas, Pulvinulinas, Nonioninas, 
Lagenas, &c., fragments of Echini, Ostracodes, Molluscs. 
Residue 87*25 per cent., consists of — 
Minerals [65'00], m. di. *3 mm., with some particles over 1 mm., 
often rounded ; quartz, often covered with oligist, augite, hornblende, 
magnetite, mica^ fragments of ancient and recent rocks.* 
* "We will not seek here to justify in detail the employment of the terms 
ancient and recent rocks, but limit ourselves to indicating the meaning which 
we give to these terms, and the reasons which have guided us in introducing 
into our descriptions this subdivision of massive crystalline rocks into two 
groups. This is not the place to enter into the discussion, which is being 
carried on at the present time among a certain number of lithologists, as to 
whether the same denomination ought to be applied to the same lithologic 
type without respect to its geological position. 
Whatever may be the issue of these discussions, it remains, nevertheless, 
true, that there exist certain minute details of structure, and certain characters 
in the constituent minerals of rocks, differences, in short, sufficiently im- 
portant to indicate generally if a massive crystalline rock belongs to ante- 
tertiary or tertiary and post-tertiary periods. If, as we think, these two 
groups can be practically distinguished, even although they present insensible 
transitions from one to the other, then it is important, for an exact knowledge 
of the origin of sediments, to take this division into consideration in our 
descriptions of marine deposits. These sediments we know include at the 
same time rocks and free minerals produced by the disintegration of these 
rocks. If we are able to apply the distinction into ancient and recent rocks, 
then we ought, in a certain sense, to be able to tell whether the isolated 
minerals found in the deposit come from the one or the other type of rock. 
We should be able, by the aid of this distinction, to determine with pro- 
bability whether the mineral fragments found in deposits come from conti- 
nents, are the result of submarine eruptions, or have been carried by floating 
ice, &c. 
Notwithstanding the care which has been taken to establish these distinc- 
tions, we are often unable to pronounce with certainty ; for, as we have said, 
the distinctive characters which we have alluded to are not so well marked, 
the fragments which are present in the deposits are very minute, and many of 
the finer details have been removed by decomposition. As to the minerals, 
with which we have more frequently to deal than with the rocks them- 
