HT. H, Howorth—Traces of a Great Post-Glacial Flood. 71 
map. Here is a whitey-brown thick-bedded felspathic rock inclosed 
between olive-green indurated beds, with ochry and grey shales, 
grits and conchoidal marls. The felspathic bed exhibits felspar 
crystals averaging 1 mm. in length. Under the microscope it is 
seen to consist of rounded quartz grains, angular fragments of 
felspar, others dull grains of whitish-yellow felsite; spherulitic 
portions in the ground seem also derived, but the outlines are not 
always distinct from the interstitial felspathic ground. 
One would suspect this bed to be a fine-grained tuff connected 
with some of the adjacent igneous rocks. I had no opportunity to 
trace these beds, which are so different from the ordinary shale of 
the district; it would be, I fear, a difficult task, as exposures seem 
so scarce. No fossils were seen here. 
V.—Traces or a Great Post-GuactaL FuLoop. 
5. EvIpENCE oF THE Marine Drirt. 
By Henry H. Howorrn, F.S.A. 
(Continued from page 16.) 
HAT is the burden of all these facts? Why, assuredly that 
the shells found in our higher marine drifts, or at least in 
neatly all of them, far from bespeaking conditions of climate such 
as can alone be fairly described as Glacial, on the contrary, speak to 
us of a time when the general temperature was perhaps somewhat 
lower than it is now, but when the North Sea and North Atlantic were 
filled with open water, and bathed a land where the Mammoth and the 
Rhinoceros could find abundant food, where the Oak and the Pine 
flourished, and where the rivers could sustain such molluscs as the 
Cyrena fluminalis. This conclusion destroys at once the basis of 
those who have argued that our high-level marine drifts were left 
where they are found by ice—either by floating bergs or a creeping 
ice-foot. But apart from the general conclusion which the particular 
collocation of shells enables us to make, quite a number of facts may 
be collected going to show the impossibility of ice having been the 
motive power which deposited such beds as those at Moel Tryfaen. 
Icebergs, if they ground, naturally crush to powder such fragile 
things as a great many shells are. This is a perfectly obvious 
ad priori criticism, but it is abundantly supported. Dr. Robert 
Brown, in describing the life near the ice fiords of Greenland, 
says, ‘In the immediate vicinity of the Jakobshavn ice fiord (and 
I take it as a type of the whole) animals living on the bottom 
were rare, except on the immediate shore, or in deep water; for 
the bergs grazed the bottom in moderately deep water to such an 
extent as almost to destroy animal and vegetable life rooted to 
the bottom. In this vicinity bunches of Algee were floating about, 
uprooted by the grounding bergs, and the dredge brought up so 
little material for the zoologist’s examination that unless in deep 
water his time was almost thrown away (Journ. Geol. Soc. vol. 
REXAaer |. OOO) 21s <. Again, in shallow inlets, except for Crustacea 
and other free-swimming animals, the bottom continually disturbed 
