255 
of Edinburgh, Session 1876-77. 
shells, say thirty foraminifera, are taken from such a deposit, and 
carefully washed, and then dissolved away with weak acid, a residue 
remains which is red-brown or grey in colour, according to the 
region from which the ooze came. If the same number of shells 
be collected from the surface and dissolved away in the same 
manner, no perceptible residue is observed. The clayey matter 
would therefore seem to have infiltrated into the shells soon after 
they fell to the bottom. 
I have already mentioned several instances of pumice-stones 
having been found on coral reefs. Many more instances could be 
given. These stones, undergoing disintegration in these positions, 
add clay, crystals of augite, hornblende, magnetic iron ore, &c., 
to the limestones which the coral animals are building up. 
I have found these crystals in the limestones and red earth of 
Bermuda, and in a specimen of the limestone from Jamaica. 
This observation, it appears to me, points out that the red earth 
of Bermuda, Bahamas, Jamaica, and some other limestones, may 
originally have been largely derived from fragmental volcanic 
materials, which were carried to the limestone while yet in the 
course of formation. There are also small particles of the peroxide 
of manganese in the red earth of Bermuda. 
Peroxide of Manganese. 
Peroxide of Manganese occurs widely in ocean deposits, either 
as nodules, incrustations, or as depositions on the bottom itself. 
It has been found most frequently in the nodular form in the deep- 
sea clays far from land. It also occurs in the organic oozes, when 
these contain much volcanic debris, or are near volcanic centres. 
In shallow water, near some volcanic islands, it covers shells 
and pieces of coral or pumice with a light brown incrustation. It 
has been met with very sparingly, if at all, in shore deposits 
removed from volcanic centres. 
In my preliminary report above referred to, I stated that further 
investigation might show that manganese nodules and depositions 
abound :in these regions where we have much of the debris of 
augitic or heavy lavas. 
A re-examination of specimens since our return confirms this 
view. Wherever we have pumice containing much magnetite, 
