418 
NATURE 
[Sept. 2, 1886 
which is the ocean I may be excused for continuing to regard 
the supposed terminal moraines of great continental glaciers as 
nothing but the southern limit of the ice-drift of a period of 
submergence. In such a period the southern margin of an ice- 
laden sea where its floe-ice and bergs grounded, or where its ice 
was rapidly melted by warmer water, and where consequently 
its burden of boulders and other debris was deposited, would 
necessarily present the aspect of a moraine, whic. by the long 
continuance of such conditions might assume gigantic dimen- 
sions. Let it be observed, however, that I fully admit the 
evidence of the great extension of local glaciers in the Pleistocene 
age, and especially in the times of partial submergence of the 
land. 
I am quite aware that it has been held by many able American 
geologists! that in North America a continental glacier extended 
in temperate latitudes from sea to sea, or at least from the 
Atlantic to the Rocky Mountains, and that this glacier must, in 
many places, have exceeded a mile in thickness. The reasons 
above stated appear, however, sufficient to compel us to seek 
for some other explanation of the observed facts, however diffi- 
cult this may at first sight appear. With a depression such as 
we know to have existed, admitting the Arctic currents along 
the St. Lawrence Valley, through gaps in the Laurentian 
watershed, and down the great plains between the Laurentian 
areas and the Rocky Mountains, we can easily understand the 
covering of the hills of Kastern Canada and New England with 
ice and snow, and a similar covering of the mountains of the 
west coast. The sea also in this case might be ice-laden and 
boulder-bearing as far south as 40°, while there might still be 
low islands far to the north on which vegetation and animals 
continued to exist. We should thus have the conditions neces- 
sary to explain all the anomalies of the glacial deposits. Even 
the glaciation of high mountains south of the St. Lawrence 
Valley would then become explicable by the grounding of floe- 
ice on the tops of these mountains when reefs in the sea. In 
like manner we can understand how on the isolated trappean 
hill of Beloeil, in the St. Lawrence Valley, Laurentian boulders 
far removed from their native seats to the north are perched at 
a height of about 1200 feet on a narrow peak where no glacier 
could possibly have left them. The so-called moraine, traceable 
from the great Missouri Coteau in the west to the coasts of 
New Jersey, would thus become the mark of the western and 
southern limit of the subsidence, or of the line along which the 
cold currents bearing ice were abruptly cut off by warm surface 
waters. I am glad to find that these considera'ions are be- 
ginning to have weight with European geologists in their ex- 
planation of the glacial drift of the great plains of Northern 
Europe. 
Whatever difficulties may attend such a supposition, they are 
small compared with those attendant on the belief of a conti- 
nental glacier, moving without the aid of gravity, and depending 
for its material on the precipitation taking place on the interior 
plains of a great continent. 
I have elsewhere endeavoured to show, on the evidence found 
in Canada, that the occurrence of marine shells, land plants, and 
insects in the glacial deposits of that country indicates not so 
much the effect of general interglacial periods as the local 
existence of conditions like those of Grinnell Land and Green- 
land, in proximity to each other at one and the same period, and 
depending on the relative levels of land and the distribution of 
ocean currents and ice-drift.? 
I am old enough to remember the sensation caused by the 
delightful revelations of Edward Forbes respecting the zones of 
animal life in the sea, and the vast insight which they gave into 
the significance of the work on minut2 organisms previously done 
by Ehrenberg, Lonsdale, and Williamson, and into the meaning 
of fossil remains. A little later the soundings for the Atlantic 
cable revealed the chalky foraminiferal ooze of the abyssal 
ocean ; still more recently the wealth of facts disclosed by the 
Challenger voyage, which naturalists have not yet had time to 
digest, have opened up to us new worlds of deep-sea life. 
The bed of the deep Atlantic is covered for the most part by 
amud or ooze largely made up of the debris of Foraminifera 
and other minute organisms mixed with fine clay. In the North 
Atlantic the Norwegian naturalists call this Biloculina mud. 
Further south the Cha//enger naturalists speak of it as Globigerina 
” 
* Report of Mr. Carvill Lewis in “ Pennsylvania Geological Survey, 
1884; also Dana's ‘‘ Manual.” 
* ““ Notes on Post-Pliocene of Canada,” 1872. One well-marked interval 
only has been established in the glacial deposits of Canada. 
ooze. In point of fact it contains different species of foraminiferal 
shells, Globigerina and Orbulina being in some localities domin- 
ant, and in others other species, and these changes are more 
apparent in the shallower portions of the ocean. 
j 
It is also to be observed that there are means for disseminat- 
ing coarse material over the ocean bed. There are in the line 
of the Arctic current on the American coast great sand-banks, 
and off the coast of Norway sand constitutes a considerable 
part of the bottom material. Soundings and dredgings off 
Great Britain, and also off the American coast, have shown that 
fragments of stone referable to Arctic lands are abundantly 
strewn over the bottom along certain lines, and the Antarctic 
continent, otherwise almost unknown, makes its presence felt to 
the dredge by the abundant masses of crystalline rock drifted 
far from it to the north. These are not altogether new dis- 
coveries. I had inferred many years ago, from stones taken up 
by the hooks of fishermen on the banks of Newfoundland, that 
rocky material from the north is dropped on these banks by the 
heavy ice which drifts over them every spring, that these stones 
are glaciated, and that after they fall to the bottom sand is 
drifted over them with sufficient velocity to polish the stones and 
to erode the shelly coverings of Arctic animals attached to them 
(‘* Notes on Post-Pliocene of Canada,” 1872). If then the 
Atlantic basin were upheaved into land we should see beds of 
sand, gravel, and boulders with clay flats and layers of marl and 
limestone. According to the Chaélenger Reports, in the Ant- 
arctic seas south of 64° there is blue mud with fragments of rock 
in depths of 1200 to 2000 fathoms. The stones, some of them 
glaciated, were granite, diorite, amphibolite, mica-schist, gneiss, 
and quartzite. This deposit ceases and gives piace to Globi- 
gerina ooze and red clay at 46° to 47° S., but even further north 
there is sometimes as much as 49 per ceat. of crystalline sand. 
In the Labrador current a block of syenite weighing 490 pounds 
was taken up from 1340 fathoms, and in the Arctic current, 100 
miles from land, was a stony deposit, some stones being 
glaciated. Among these were smoky quartz, quartzite, lime- 
stone, dolomite, mica-schist, and serpentine ; also particles of 
monoclinic and triclinic feldspar, hornblende, augite, magnetite, 
mica, and glauconite, the latter no doubt formed in the sea- 
bottom, the others drifted from Fozoic and Palaeozoic formations 
to the north (‘* General Report, Crallenger Expedition”), 
A remarkable fact in this connection is that the great depths 
of the sea are as impassable to the majority of marine animals 
as the land itself. According to Murray, while twelve of the 
Challengers dredgings taken in depths greater than 2000 fathoms 
gave 92 species, mostly new to science, a similar number of 
dredgings in shallower water near the land gave no less than 
1000 species. Hence arises another apparent paradox relating 
to the distribution of organic beings. While at first sight it 
might seem that the chances of wide distribution are exception- 
ally great for marine species, this is not so. Except in the case 
of those which enjoy a period of free locomotion when young, 
or are floating and pelagic, the deep ocean sets bounds to their 
migrations. On the other hand, the spores of cryptogamic 
plants may be carried for vast distances by the wind, and the 
growth of volcanic islands may effect connections which, though - 
only temporary, may afford opportunity for land animals and 
plants to pass over. 
But I must here call your attention to still another geological 
paradox, namely, that the deep sea, which is so great a barrier 
to the passage of the shallow-water animals, seems, under 
certain conditions, to afford facilities for the transmission of land 
animals and plants. ‘The connections established by the obser- 
vations of the Chadlenger, and so well expounded by Wallace 
and Hemsley (‘‘ Continental and Island Life” ; ‘‘ Botany of the 
Challenger Expedition’), between the floras of oceanicislands and 
the continents, establish this conclusively. Thus the Bermudas, 
altogether recent islands, have been stocked by the agency chiefly 
of the ocean currents and of birds, with nearly 150 species of 
continental plants, and the facts collected by Hemsley as to the 
present facilities of transmission, along with the evidence afforded 
by older oceanic islands which have been receiving animal and 
vegetable colonists for longer periods, go far to show that, time 
being given, the sea actually affords facilities for the migra- 
tions of the inhabitants of the land, greater than those of 
continuous continents. 
With reference to the transmission of living beings across the 
Atlantic, we have before us the remarkable fact that from the 
Cambrian age onwards there were on the two sides of the 
ocean many species of invertebrate animals which were either 
