24 Proceedings of the Royal Physical Society. 
laid down in the deep sea. We have, for instance, no 
positive ground for supposing that the abundant presence of 
manganese is an absolutely essential character of the waters 
of the deep sea; and we know, for certain, that sharks have 
not always existed, and that the presence of the teeth of 
shark-like fishes is assuredly not to be looked for as a con- 
stant feature in deep-sea muds. Thus, Neumayr has pointed 
out that in the Upper Jurassic series of the Alps and Car- 
pathians there exists over large areas a white or light grey 
limestone associated with hornstones (? Radiolarian cherts), 
which contains hardly any other fossils than the so-called 
“ Aptychi” of Ammonites; while the shells of the Ammonites 
themselves are, as a rule, wanting. Associated with these 
limestones in places are red clays richly charged with Aptychz. 
Neumayr regards the whole series as of deep-water origin, 
and compares the red clays with Aptychi to the modern red 
clays with Carcharodon teeth. He also regards as of deep- 
water origin a red limestone with Ammonites which occurs 
in the Trias and Jurassic series of the Alps, and which in 
places contains small nodules of manganese (“Hrdgeschichte,” 
p. 364). He suggests, moreover, that the red “ Orthoceras 
limestone” of the Ordovician series of Northern Europe 
may likewise be of deep-water origin. 
GEOLOGICAL STRUCTURE OF OCEANIC ISLANDS. 
I have dealt in some detail with the assertion that no 
deposits analogous to the deep-sea deposits of the present 
day occur in the present dry lands, because I regard this as 
embodying the one fundamental argument which can be 
brought forward in favour of the doctrine of the “ perman- 
ence of the ocean-basins.” The few remaining arguments in 
favour of the same doctrine I must pass over with very 
scanty notice. One of the most important of these is based 
on the assertion that “ oceanic” islands, and particularly the 
smaller ones which rise out of the deeper and larger oceans, 
are not formed of crystalline or sedimentary rocks, as they 
would probably be if they were the surviving peaks of a 
submerged continent, but that they are either volcanic in 
