332 
THE VOYAGE OF H.M.S. CHALLENGER. 
Examination in convergent light does not give precise indications concerning other 
optic phenomena that might be used for a more exact determination of the species. 
The blackish brown inclusions represented in figs. 10 and 13 present vaguely regular 
contours, recalling crystallites, such as magnetite, found in eruptive rocks and in 
certain slags. In fig. 10, where they are seen under a magnifying power of about 
300 diameters, they have a crystalline aspect ; in all probability these inclusions are 
magnetic, more or less titaniferous, iron, and their presence explains why these spherules 
may be extracted from the mud by the aid of a magnet. It will be observed that 
these dark-coloured inclusions are disposed in a parallel manner following the system 
of lamellse, and that they remain constant in this direction, even in thin plates. 
At certain points they are so abundant as to completely veil by their accumulation 
the structure of the mineral "with which they are associated, as represented in the upper 
part of fig. 13. This regular arrangement of the inclusions in the interior of the 
lamellae shows an approach to minerals belonging to the group of rhombic pyroxenes. 
It is known that the species of this group richest in iron contain tabular or prismatic 
inclusions of a submetallic and very characteristic aspect. Enstatite, bronzite, and 
even hypersthene, which constitute chondres, are of the rhombic system, but we have 
just seen that the mineral constituting these brown spherules belongs to the monoclinic 
system, perhaps, to judge from the extinctions, to a monoclinic pyroxene. Up to the 
present time, it must be added, no chondres have been found with other than rhombic 
pyroxenes, so that there is an important difference between these spherules and the 
chondres, if our determination of the mineral of the spherules as belonging to the 
monoclinic system be correct. There would, however, be nothing astonishing in the 
existence of chondres with monoclinic pyroxene, as this mineral is known to exist, for 
example, in eukrite, and it must be remembered that only a small number of the brown 
spherules found in the deposits were examined for their optical properties. 
The external characters of these spherules, their bronze colour with metallic lustre, 
their excentric lamellar structure, in a word, all their properties, except the difference 
revealed by optical examination, show profound analogies between these spherules and the 
chondres of meteorites, so that we seem justified in attributing to them a cosmic origin, 
and this opinion is confirmed by tlieir association with the black magnetic spherules and 
their distribution over the floor of the ocean, which will now be referred to in greater 
detail. 
(c.) Distribution of Cosmic Spheimles in Marine Deposits. 
Magnetic or cosmic spherules were found in greatest abundance in the Red Clays 
of the Central and Southern Pacific ; in short, in the deepest water, at points furthest 
removed from continenUil masses of land. When the magnetic particles are extracted 
from about a quart of the clay from these regions, it is usual to observe among these 
