514 Proceedings of the Royal Society 
istic decompositions which there take place are associated with 
pyroxenic lavas. 
Associated with the red clay are almost always found concretions 
and microscopic particles of the oxides of iron and manganese, 
to which the deposit owes its colour. Again, in the typical 
examples of the deposit, zeolites in the form of crystals and 
crystalline spherules are present, along with metallic globules 
and silicates which are regarded as of cosmic origin. Calcareous 
organisms are so generally absent in the red clay that they cannot he 
regarded as characteristic ; when present they are chiefly the shells 
of pelagic Foraminifera, and are usually met with in greater numbers 
in the surface layers of the deposit, to which they give a lighter 
colour. On the other hand, the remains of Diatoms, Eadiolarians, 
and sponge spicules are generally present, and are sometimes very 
abundant. The ear-bones of various cetaceans, as well as the 
remnants of other cetacean bones, and the teeth of sharks, are, in 
some of the typical samples far removed from the continents, ex- 
ceedingly abundant, and are often deeply impregnated with, or 
embedded in thick coatings of, oxides of iron and manganese. The 
remains of these vertebrates have seldom been dredged in the 
organic oozes, and still more rarely in the terrigenous deposits. 
The fine washings^ as examined with a power of 450 diameters, 
are composed of an amorphous matter, fragments of minerals, 
the remains of siliceous organisms, and colouring substances. 
What we call amorphous matter may be considered as properly 
the argillaceous matter, and presents characters essentially vague. 
It appears as a gelatinous substance, without definite contours, 
generally colourless, perfectly isotropic, and forms the base which 
agglutinates the other particles of the washings. As these physical 
properties are very indefinite, it is difficult to estimate even approxi- 
mately the quantity present in a deposit. However, it augments in 
proportion as the deposit becomes more clayey, but we think that 
only a small quantity of this substance is necessary to give a clayey 
character to a deposit. Irregular fragments- of minerals, small 
pieces of vitreous rocks, and remains of siliceous organisms pre- 
dominate in this fundamental base. These particles probably 
make up about 50 per cent, of the whole mass of the fine ivasliings^ 
and this large percentage of foreign substances must necessarily 
