of the Island of St. Paul. 365 
island resembles Kieselguhr, and consists chiefly of Phytolitharia, 
is black when moist, brown when dry ; but in the vicinity of the 
fumaroles it is often of a bright ochreous rusty red (Nos. 6,7,8). 
By ignition, the black earths become not red, but white. The 
iron is therefore no constituent of the Phytolitharia, but an ex- 
traneous constituent introduced no doubt by the volcanic fuma- 
roles. If the rusty-red earth, which, as reported, appears here 
and there to be a product of the weathering of bog iron-ore 
and brown ironstone, behaves everywhere like the samples, we 
are compelled, on account of its organic composition, to reverse 
the notion, and to regard the rocks standing in connexion with 
such earths as consisting of the latter repeatedly baked, hardened 
and metamorphosed. 
The slight mixture of the Phytolitharian humus with in- 
organic sand and volcanic ashes appears of importance. From 
this we may undoubtedly draw many conclusions as to the acti- 
vity of the volcano. If the average annual mass of the humus 
can be ascertained, we shall be able to judge approximately, from 
the thickness of the earthy mound, of the last period of repose 
of the voleano. Showers of ashes must have immediately effected 
a great change in such pure Phytolitharian humus. The sam- 
ples, however, relate to considerable depths in the mass, and not 
to the immediate surface. 
Further, the earths and rocks investigated allow us to express 
the opinion that the looser earthy coverings of the mound, 
whether black or red, are freshwater formations. With the ex- 
ception of No, 5, all the marine forms registered are from points 
on the shore within high water. No considerable action of the 
sea upon the soil produced by the grassy vegetation and the up- 
permost rocks dependent upon this is anywhere indicated by the 
intermixture of marme forms; consequently the union of the 
crater-lake with the outer sea, produced since the year 1697, 
cannot lead us to the conclusion that a rising and swell of the 
sea touching the upper part of the land has formerly taken 
lace. 
The rock No. 5 from the upper margin of the crater (846 ft.) 
appears to be particularly interesting. It resembles a bog 
iron-ore, and has been so described by me. From its rich 
marine organic admixture, it appears to me, in the midst of the 
freshwater formations, as the ancient sea-bed, which the volcano 
has forced up, with little change at the time of its elevation, 
and impregnated with oxide of iron. Perhaps other materials 
in the collections of the ‘ Novara’ may furnish further evidence, 
especially as to the thickness of the mass. 
It is eight years since I registered, from Kerguelen’s Land, 
situated still further towards the south pole, 56 microscopic 
