20 Proceedings of the Royal Physical Society. 
age. Itis interesting to note that the Radiolarian cherts 
of Mullion Island, like those of Saxony and Lanarkshire, 
are associated with “ greenstones,” having a characteristic 
“spheroidal” structure; and Mr Teall even throws out the 
suggestion that this peculiar structure may perhaps be 
“characteristic of submarine and possibly deep-sea lavas ” 
(“On Greenstones associated with MRadiolarian Cherts,” 
Trans. Roy. Geol. Soc. of Cornwall, 1894). 
Barrois, again, has recently announced the discovery of 
Radiolarian cherts in strata of supposed pre-Cambrian age 
in Brittany (Comptes Rend. Acad. Sct., vol. cxv., p. 826, 1892). 
There can, therefore, be no doubt as to the wide distribution 
of these deep-sea cherts in the early Paleozoic rocks of the 
European area; and there is the absolute certainty that, now 
attention has been directed to the point, further investiga- 
tions will show that these peculiar deposits have in reality 
amuch more extended range than would a few years ago 
have been believed. We arrive thus at the conclusion that, 
so far from the seas of the Ordovician period having been 
uniformly shallow, true deep-water conditions prevailed 
during some portion of this epoch, over, at any rate, an 
extensive area in Europe. It does not seem to me possible 
to evade this conclusion, except by the adoption of the 
wholly illogical position that the Radiolarian oozes of the 
existing oceans are of deep-water origin, but that, as it is 
believed that the dry land is wholly made up of shallow- 
water deposits, therefore all Radiolarian deposits occurring 
in the dry land—however similar to those of the present 
day—must, ex hypothesi, be also of shallow-water origin. 
Leaving the Ordovician and earlier periods, Rothpletz has 
shown the occurrence of Radiolarians in the Silurian (Joe. cit., 
supra), and Riist has proved that characteristic Radiolarian 
cherts occur in the Devonian and Carboniferous rocks of 
Europe; while, as before said, we have ample proof of the 
existence of Radiolarian deposits in the Mesozoic series. It 
is, however, in the latter portion of the Tertiary period that 
we find these Radiolarian deposits most largely developed 
and most unequivocal in character. Such deposits occur in 
the Tertiaries of various parts of Southern Europe, in the 
