1890 - 91 .] Mr J. Y. Buchanan on Sulphur in Marine Muds. 19 
characteristics of those from the greatest depths of the open ocean; 
and this similarity was maintained on chemical examination. The 
dredging anchor must on this occasion have heen dropped in the 
very richest part of the deposit ; for the mud, which had undergone 
no concentrating process, was found, on being submitted to mechani- 
cal analysis, to consist of rather over 30 per cent, of nodules.* This 
was a very remarkable discovery ; for although peroxide of manganese 
was not wanting in the shallower dredgings of the “ Challenger,” it 
existed only as coatings and similar deposits and not as nodules, 
which were believed to he dependent for their formation on the 
conditions obtaining in very deep water. After this particular 
attention was paid to the occurrence of manganese in all dredgings, 
and it was found to be abundant all round our coasts as a coating 
on shells, and more especially as the binding and colouring matter 
of worm tubes ; but no nodules were anywhere found except in the 
deep part of Loch Tyne. Some years afterwards Mr Murray found 
them in great abundance on the Skelmorlie Bank in the Firth of 
Clyde in 10 fathoms. 
In the same summer of 1878 I made a number of observations in 
the channel off the north-east part of the Island of Arran, where the 
water reaches a depth of 90 fathoms. A galvanised iron bucket was 
used as dredge, with a weight attached behind, and one before it ; 
so that its action was rather to skim the surface than to dig into 
the lower layers of the bottom. It brought up a quantity of a very 
fine red mud, in which manganese grains could he detected, not 
apparently differing from those found in oceanic red clays. In the 
process of levigation, when the mud was stirred up with water and 
the light flocculent portion poured off, the heavier portion which 
had settled to the bottom of the vessel had the appearance of having 
heen cast into elongated pellets. When these were stirred up again 
with water they were partially broken up into flocculent matter, 
which was poured off, leaving again pellets as before; and this could 
he continued until the whole of the mud had heen washed away as 
flocculi, produced by the breaking up of these pellets. In the case 
of the particular mud under description, hardly anything in the 
shape of sand or coarser material remained behind. The ground- 
fauna, chiefly ophiurids, seemed to he abundant ; and the pellets 
* Nature , 1878 , vol. xviii. p. 628 . 
