492 Proceedings of the Eoycd Society 
is protected from further oxidation by the coating which thus covers 
it. 
One may suppose that meteorites in their passage through the 
atmosphere break into numerous fragments, that incandescent 
particles of iron are thrown off all round them, and that these 
eventually fall to the surface of the globe as almost impalpable dust, 
in the form of magnetic oxide of iron more or less completely 
fused. The luminous trains of falling stars are probably due to the 
combustion of these innumerable particles resembling the sparks 
which fly from a ribbon of iron burnt in oxygen, or the particles of 
the same metal thrown off when striking a flint. It is easy to show 
that these particles in burning take a spherical form, and are sur- 
rounded by a layer of black magnetic oxide. 
Among the magnetic grains found in the same conditions as these 
we have just described are other spherules, which we refer to the 
cliondres, so that if the interpretation of a cosmic origin for the 
magnetic spherules with a metallic centre were not established in a 
manner absolutely beyond question, it almost becomes so when we 
take into account their association with the silicate spherules, of 
which we have now to speak. It will be seen by the micro- 
scopic details that these spherules have quite the constitution 
and structure of chondres so frequent in meteorites of the most 
ordinary type, and on the other hand they have never been found, 
as far as we know, in rocks of a terrestrial origin; in short, the 
presence of these spherules in the deep sea deposits, and their 
association with the metallic spherules, is a matter of prime 
importance. Let us see how we distinguish these silicate 
spherules, and the points upon which we rely in attributing 
to them a cosmic origin. 
Among the fragments attracted by the magnet in deep sea 
deposits we distinguish granules slightly larger than the spherules 
with the shining black coating above described. These are yellowish- 
brown, with a bronze-like lustre, and under the microscope, it is 
noticed that the surface, instead of being quite smooth, is 
grooved by thin lamellae. In size they never exceed a milli- 
metre, generally they are about 0'5 mm. in diameter; they are 
never perfect spheres, as in the case of the black spherules with a 
metallic centre ; and sometimes a depression more or less marked 
