Sept. 2, 1886 | 
NATURE 
415 
the sea ; while it is also to be noted that there are, as already 
stated, bordering shelves, constituting shallows in the ocean, 
which at certain periods have emerged as land. 
We are thus compelled to believe in the contemporaneous ex- 
istence in all geological periods, except perhaps the earliest of 
them, of three distinct conditions of areas on the surface of the 
earth. (1) Oceanic areas of deep sea, which always continued 
to occupy in whole orin part the bed of the present ocean. (2) 
Continental plateaus and marginal shelves, existing as low flats 
or higher table-lands liable to periodical submergence and emer- 
gence. (3) Lines of plication and folding, more especially along 
the borders of the oceans, forming elevated portions of land, 
rarely altogether submerged, and constantly affording the mate- 
rial of sedimentary accumulations, while they were also the seats 
of powerful volcanic ejections. 
In the successive geological periods the continental plateaus 
when submerged, owing to their vast extent of warm and shal- 
low sea, have been the great theatres of the development of 
marine life and of the deposition of organic limestones, and 
when elevated they have furnished the abodes of the noblest 
land faunas and floras. The mountain belts, especially in the 
north, have been the refuge and stronghold of land life in periods 
of submergence, and the deep ocean basins have been the peien- 
nial abodes of pelagic and abyssal creatures, and the refuge of 
multitudes of other marine animals and plants in times of con- 
tinental elevation. These general facts are full of importance 
with reference to the question of the succession of formations 
and of life in the geological history of the earth, 
So much time has been occupied with these general views 
that it would be impossible to trace the history of the Atlantic 
in detail through the ages of the Palaeozoic, Mesozoic, and 
Tertiary. We may, however, shortly glance at the changes of 
the three kinds of surface already referred to. The bed of the 
ocean seems to have remained on the whole abyssal, but there 
were probably periods when those shallow reaches of the Atlantic 
which stretch across its most northern portion, and partly 
separate it from the Arctic basin, presented connecting coasts 
or continuous chains of islands sufficient to permit animals and 
plants to pass over. At certain periods also there were not 
unlikely groups of volcanic islands, like the Azores, in the 
temperate or tropical Atlantic. More e pecially might this be 
the case in that early time when it was more hke the present 
Pacific ; and the line of the great volcanic belt of the Mediter- 
ranean, the mid-Atlantic banks, the Azores, and the West India 
Islands point to the possibility of such partial connections, These 
were stepping stones, so to speak, over which land organisms 
might cross, and some of these may be connected with the 
fabulous or prehistoric Atlantis.” 
In the Cambrian and Ordovician periods the distinctions, 
already referred to, into continental plateaus, mountain-ridges, 
and ocean depths were first developed, and we find already great 
masses of sediment accumulating on the seaward sides of the old 
Laurentian ridges, and internal deposits thinning away from 
these ridges over the submerged continental areas, and pre- 
senting very dissimilar conditions of sedimentation. It would 
seem also that, as Hicks has argued for Europe, and Logan and 
Hall for America, this Cambrian age was one of slow subsidence 
of the land previously elevated, accompanied with or caused by 
thick deposits of detritus along the borders of the subsiding land, 
which was probably covered with the decomposing rock arising 
from long ages of sub-aérial waste. 
In the coal-formation age, its characteristic swampy flats 
stretched in some places far into the shallower parts of the 
ocean. Inthe Jurassic the American continent probably ex- 
tended further to sea than at present. In the Wealden age 
there was much land to the west and north of Great Bricain, and 
Prof. Bonney has directed attention to the evidence of the 
existence of this land as far back as the Trias, while Mr. Starkie 
Gardner has insisted on connecting-links to the southward, as 
* Tt would seem, from Geikie’s description of the Faroe Islands, that they 
may bea remnant of such connecting land, dating from the Cretaceous or 
Eocene period. 
* Dr. Wilson has recently argued that the Atlantis of tradition was really 
America, and Mr. Hyde Clark has associated this idea with the early domin- 
ance in Western Europe of the Iberian race, which Dawkins connects with 
the Neolithic and Bronze Ages of archaology. My own attention has 
recently been directed, through specimens presented to the McGill College 
Museum, to the remarkable resemblances in cranial characters, wampum, 
and other particulars, of the Guanches of the Canaries with aborigines of 
Eastern Amer.ca —resemblances which cannot be accidental. 
> I have shown the evidence of this in the remnants of Carboniferous 
districts once more extensive on the Atlantic coast of Nova Scotia and Cape 
Rreton (“ Acadian Geology ’’). 
evidenced by fossil plants. So late as the post-Glacial, or early 
human period, large tracts now submerged formed portions of 
the continents. On the other hand, the internal plains of America 
and Europe were often submerged. Such submergences are 
indicated by the great limestones of the Palzozoic, by the chalk 
and its representative beds in the Cretaceous, by the Nummulitic 
formation in the Eocene, and lastly by the great Pleistocene 
submergence, one of the most remarkable of all, one in which 
nearly the whole northern hemisphere participated, and which 
was probably separated from the present time by only a few 
thousands of years.! These submergences and elevations were 
not always alike on the two sides of the Atlantic. The Salina 
period of the Silurian, for example, and the Jurassic, show con- 
tinental elevation in America not shared by Europe. ‘The great 
subsidences of the Cretaceous and the Eocene were proportion- 
ally deeper and wider on the eastern continent, and this and the 
direction of the land being from north to south cause more 
ancient forms of life to survive in America. These elevations 
and submergences of the plateaus alternated with the periods of 
mountain-making plication, which was going on at intervals at 
the close of the Eozoic, at the beginning of the Cambrian, at 
the close of the Siluro-Cambrian, in the Permian, and in Europe 
and Western America in the Tertiary. The series of changes, 
however, affecting all these areas was of a highly complex 
character, and embraces the whole physical history of the 
geological ages. 
We may note here that the unconformities caused by 
these movements and by subsequent denudation constitute what 
Le Conte has called ‘‘lost intervals,” and one of the most 
important of which is supposed to have occurred at the end of 
the Eozoic. It is to be observed, however, that as every such 
movement is followed by a gradual sub-idence, the seeming loss 
is caused merely by the overlapping of the successive beds 
deposited. 
We may also note a fact which I have long ago insisted on 
(‘* Acadian Geology,” 1865), the regular pulsations of the con- 
tinental areas, giving us alternations in each great system of 
formations of deep-sea and shallow-water beds, so that the 
successive groups of formations may be divided into triplets of 
shallow-water, deep-water, and shallow-water strata, alternating 
in each period. 
In referring to the ocean basins we should bear in mind that 
there are three of these in the northern hemisphere—the Arctic, 
the Pacific, and the Atlantic. De Rance has ably summed up 
the known facts as to Arctic geology, and more recently Dr. G. 
M. Dawson has prepared for the Royal Society of Canada a 
résumé and map of what is known of the geology of the Arctic 
basin (meeting of May 1886; the paper is not yet published), 
in comparison with Canadian geology. From this it ap- 
pears that this area presents from without inwards a succession 
of older and newer formations from the Eozoic to the Tertiary, 
and that its extent must have been greater in former periods than 
at present, while it must have enjoyed a comparatively warm 
climate. The relations of its deposits and fossils are closer with 
those of the Atlantic than with those of the Pacific, as might be 
anticipated from its wider opening into the former. Blandford 
has recently remarked on the correspondence of the marginal 
deposits around the Pacific and Indian Oceans,” and Dr. Dawson 
informs me that this is equally marked in comparison with the 
west coast of America,* but these marginal areas have not yet 
gained much on the ocean. In the North Atlantic, on the other 
hand, there is a wide belt of comparatively modern rocks on 
both sides, more especially toward the south, and on the Ameri- 
can side ; but while there appears to be a perfect correspondence 
on both sides of the Atlantic and around the Pacific respect- 
I The recent surveys of the Falls of Niagara coincide with a great many 
evidences to which I have elsewhere referred in proving that the Pleistocene 
submergence of America and Europe came to an end not more than ten 
thousand years ago, and was itself not of very great duration. Thus in 
Pleistocene times the land must have been submerged and re-elevated in a 
very rapid manner. ; 
2" A singular example is the recurrence in New Zealand of ‘Triassic rocks 
and fossils of types corresponding to those of British Columbia. A curious 
modern analogy appears in the works of art of the Maoris with those of the 
Haida Indians of the Queen Charlotte Islands, and both are eminently Pacific 
in contradistinction to Atlantic. 
3 Journal of Geological Society, May 1586. Blandford’s statements 
respecting the mechanical deposits of the close of the Palaozoic in the Pacific 
area, whether these are glacial or not, would seem to show a ccrrespondence 
with the Permian conglomerates and earth-movements of the Atlantic area; 
but since that time the Atlantic has enjoyed comparative repose. The Pacific 
also seems to have reproduced the conditions of the Carboniferous in the 
Cretaceous age, and seems to have been less affected by the great changes of 
| the Pleistocene. 
