THE ICE AGE. CLIMATE AND TIME. 
243 
-of climate to which we have been referring, and without doubt 
they would do so ; but it is now generally agreed that little or no 
such change has taken place, and that all our large continents 
and islands not only existed in the glacial epoch, as they do now, 
but that the very contour of the Earth’s surface was pretty much 
the same then as it is now. If an island, a 66 New Atlantis,” 
ever existed between the British Isles and America— cutting off 
the influence of the Gfulf Stream — there is no doubt the con- 
ditions of our climate would be greatly altered. But there is 
no evidence of any such island ever having existed. We are 
therefore driven back to an examination of the influence of the 
increase of eccentricity ; and although it could not directly lower 
the temperature of our country and cover it with ice, yet it might 
bring into operation physical agents which would produce this 
result. The argument of “ Climate and Time ” is, that a high 
state of eccentricity would produce deflections of the ocean 
currents, and materially modify their effects, thus producing 
variations of climate upon the continents and islands within 
the influence of their waters. To such an extent is the tempera- 
ture of the equatorial regions lowered, and that of temperate 
and polar regions raised, by means of ocean currents, that were 
they to cease, and, each latitude to depend solely on the heat 
received directly from the sun, only a very small portion of the 
globe would be habitable by the present order of beings. 
Although it has been contended by Arago, Humboldt and 
others, that climatic variation is but very slightly influenced by 
changes in the elliptical form of the Earth’s orbit, yet there is 
every reason for believing that the oceanic currents do suffer de- 
flection by such changes. Consequently, if the Gfulf Stream were 
stopped in its circulation northward, and if the heat conveyed 
by its waters was deflected into the Southern Ocean, this would 
enormously lower the temperature of the northern hemisphere, 
and elevate it in a corresponding degree to the south of the 
equator. 
With the physical causes of oceanic circulation, it is not at 
present possible to deal. There are two theories which attempt 
to account for it — one referring the circulation to the influence 
of wind, and the other to the effect of gravitation . The relation 
which these hypotheses bear on the question of the changes of 
climate, may be made clear in a few words. When the eccen- 
tricity of the Earth’s orbit attains a high value, the hemisphere, 
whose winter solstice occurs in aphelion, has its temperature 
lowered, while that of the opposite hemisphere is raised. If we 
suppose the northern hemisphere to be the cold one and the 
southern the warm one, the difference of temperature between 
the equator and the north pole will then be greater than between 
the equator and the south pole. If the circulation of oceanic 
