Cause of the Glacial Period 
The rapid fall from 48° to 33° F. was due to the Baffin’s Bay cold current. 
Now, assuming Professor Hull’s statement of the lowering of the temperature due to the deflection of the 
Gulf Stream owing to the elevation of the Antillean continent, the temperature of the waters of the Gulf of St. 
Lawrence Gre Hh So WELT month as September would be lowered from 33° to 23°. The St. Lawrence and adjacent 
seas would be ice-bound, and icebergs would be set adrift, to float even farther southward (probably 1000 miles) than at 
present the Greenland bergs do, with a correspondingly lowering influence upon the temperature of sea and air. 
Judging from the influence of a large number of bergs adrift in the North Atlantic, in producing damp and cheerless 
summers in the British Isles, e.g. 1877, 1878, 1879, etc., such conditions as Professor Hull supposes would make 
summer in these islands a thoroughly “ glacial” one. 
Judging from what I saw of geological phenomena in Connecticut in October last, the glacial conditions farther 
south were even more rigorous than my estimate indicates. 
Professor Newcombe and Rev. E. Hill are dissatisfied as astronomers with the astronomical explanation of the 
cause of the Glacial epoch. Sir Joseph Prestwich! has fully discussed the question of recurring glaciations, which 
Croll’s hypothesis renders necessary, rejecting these glaciations as facts, either (1) from want of evidence, or (2) because 
the geological evidence is all the other way.? As this and various other astronomical theories are unable to bear the 
strain put upon them, we must, I think, conclude that some geographical explanation is the more probable ; and that, as 
an uplift such as Professor Hull postulates would be attended by glacial conditions, his theory, or some modification 
of it, may be accepted as best satisfying all the conditions of the problem. 
The Rev. G. Crewpson, M.A., writes :— 
Fanuary 18th, 1898. 
May I be allowed to suggest a few considerations which seem to confirm the theory which Professor Hull has so 
ably expounded in his paper on “ Another Possible Cause of the Glacial Epoch.” 
In the present day it will be observed that owing to the Antarctic cold the stream of heated equatorial water is 
pressed northwards, a greater breadth of the stream being north of the Equator than south of the line ; consequently a 
larger proportion of water is diverted northwards at Cape S. Roque than would be the case if the stream were accurately 
equatorial. 
If, however, Arctic conditions were to prevail in the North Atlantic, these conditions would be reversed, and a 
much larger amount of heated water would be diverted into the Brazilian current flowing southwards than is at present 
the case, and the North Atlantic would receive less than its due share. This would not only lessen the amount 
of heat available for raising the temperature of the northern regions, but would also diminish the resistance that would 
be offered to cold currents from the Arctic Ocean ; a point which receives increased importance from the consideration 
of possible changes in the Pacific area. 
For there is another fact which can scarcely be said to be less than paradoxical in its character, that at the time 
when Northern Europe and Eastern North America were enduring a climate of exceptional rigour, Siberia and Western 
North America were enjoying a comparatively temperate climate. Somehow or other, therefore, warm winds must 
have been able to find their way into the Arctic regions in that hemisphere at the same time that they were excluded 
from the European area. Now at the present day Behring Straits are narrow and shallow, and little or no water is able 
to enter from the Pacific equatorial current. But with the exception of the mountains to the south of Alaska, the land 
bordering the strait is, generally speaking, low and alluvial. If then this were depressed, a large free access would be 
opened to the Arctic Ocean on that side ; and if this were the case I do not think it unreasonable to suppose that a 
stronger and more highly heated current would pass through than is found in the Gulf Stream, inasmuch as the Pacific 
is larger than the Atlantic, and the northward-flowing stream would not have to contend with any counter-flowing 
current, all the water finding its exit by way of the Atlantic channel. It is obvious that by the time the water had 
reached the Scandinavian coast it would have lost all its heat, and would very largely contribute to further reduce the 
temperature in the North Atlantic area; and being comparatively unopposed in its southward course, and pressed 
forward by the floods from the Pacific, it would probably develop a force far exceeding that of the existing Greenland 
current; a force that would be sufficient in fact to produce those perplexing glacial markings in Scandinavia and 
elsewhere which Mr. Lindvall has ascribed with much probability to the action of drift-ice rather than that of a sheet 
of land-ice. 
It is true that the tendency of the south-flowing Arctic current would be to trend towards the Greenland side of the 
channel, owing to the effects of the revolution of the earth on its axis ; but if Greenland shared, as it probably did, in 
the general elevation of the east coast of America, the current would be driven more towards the European shore, and 
the course of the Gulf Stream itself is an evidence that currents can be diverted by geographical or other causes into 
other than their natural channels. 
This theory also meets another difficulty. Great cold does not necessarily mean abundant snow. A region of 
evaporation at no great distance is also necessary. A heated Siberian sea would afford just such an area as would be 
needed to produce a heavy snowfall in North-West Europe and North-East America. We should thus have every 
condition for producing a Glacial epoch in these regions. 
This seems to me to supply a simple explanation of this remarkable era, without calling in the help of a Deus ex 
2 Prestwich, Controverted Questions in Geology, p. 23. 
39 
1 Prestwich, Geohgy, ii. p. 527, note. 
