of Edinburgh, Session 1876 - 77 . 261 
First, That volcanic debris, either in the form of pumice stones, 
ashes, or ejected fragments, are universally distributed in ocean 
deposits. 
Second, That pumice stones are continually being carried into 
the sea by rivers and rains, and are constantly floating on the sur- 
face of the ocean far from land. 
Third, That the clayey matter in deposits far from land is prin- 
cipally derived from the decomposition of the feldspar in fragmental 
volcanic rocks, though in the trade wind region of the North 
Atlantic the dust of the Sahara contributes much material for 
clay. 
Fourth, That the red earth of Bermuda, Bahamas, Jamaica, 
and other limestone countries, is most probably originally derived 
from the decomposition of pumice stone, while these limestones 
were in the process of formation. 
Fifth, That the peroxide of manganese is probably a secondary 
product of the decomposition of the volcanic rocks and minerals 
present in the areas where the nodules of manganese are found. 
Sixth, That there are many minute particles of native iron in 
deposits far from land; that some of these particles are little sphe- 
rules ; that these last, as well as some other spherules which are 
magnetic, have probably a cosmic origin. 
Seventh , That the peroxide of manganese depositions in the 
deep sea are different in structure and composition from known 
ores of manganese. 
Eighth . — That we do not appear to have equivalents of the rocks, 
now forming in the deep sea far from land, in the geological series. 
In conclusion, I have to acknowledge much assistance in these 
investigations from all my colleagues, especially my indebtedness to 
Sir Wyville Thomson and Mr Buchanan. 
Since my return I have received many hints from Professors Tait, 
Gfeikie, Turner, Dr Purves, Mr Morrison, and other gentlemen. 
In much of the mechanical work which an examination of these 
b 
deposits has entailed, I have, both during the cruise and since my 
return, had the assistance of Frederick Pearcey. 
