at others."<14> We have just seen that the earth is nearer the sun at
one time of the year than at another. At present the earth passes its
perihelion point in the Winter of the Northern Hemisphere, and its
aphelion point in the Summer. We will for the present suppose that it
always reaches the points at the same season of the year. Let us see if
the diminished distance from the sun in Winter has any thing to do with
the climate.

If so, this effect will be greatly magnified during a period of high
eccentricity, such as the earth has certainly passed through in the
past. We will state first, that the more elliptical the orbit becomes,
the longer Summer we have, and the shorter Winter. Astronomically,
Spring begins the 20th of March, and Fall the 22d of September. By
counting the days between the epochs it will be found that the Spring
and Summer part of the year is seven days longer than the Fall and
Winter part. But if the earth's orbit becomes as highly eccentrical as
in the past, this difference would be thirty-six days.<15>

This would give us a long Spring and Summer, but a short Fall and
Winter. This in itself would make a great difference. We must beer in
mind, however, that at such a time as we are here considering, the earth
would be ten millions of miles nearer the sun in Winter than at present.
It would certainly then receive more heat in a given time during Winter
than at present.<16> Mr. Croll estimates that whereas the difference in
heat received during a given time is now one-fifteenth,<17> at the time
we are considering it would be one-fifth. Hence we see that at such a
time the Winter would not only be much shorter than now, but at the same
time would be much milder.

These are not all the results that would follow an increase of
eccentricity. The climate of Europe and North America is largely
modified by those great ocean currents--the Gulf Stream and the Japan
current. Owing to causes we will not here consider, these currents
would be greatly increased at such a time. As a result of these combined
causes, Mr. Croll estimates that during a period of high eccentricity
the difference between Winter and Summer in the Northern Hemisphere
would be practically obliterate. The Winter would not only be short,
but very mild, and but little snow would form, while the sun of the long
Summers, though not shining as intense as at present, would not have to
melt off a great layer of snow and ice, but the ground b