0 did not equal that from 1815 to 1820, nor indeed those of 1775 to
1780 or 1795 to 1800. But as these variations, so far as we are enabled to
judge, depend upon the varying influence of the sun's rays, and of
volcanic action, it is impossible to say that equally cold periods will
not return, during the latter half of this century.

If the influence of the sun was constant, and volcanic action regular, two
causes would tend to modify the seasons:

1st. The exposure of the surface to a more effective action of the solar
rays, by a removal of the forests, and by drainage. That such action would
be more effective upon a surface thus uncovered and drained, can not be
doubted.

2d. _The movement of the area of magnetic intensity, and the magnetic
pole, to the west._--There is such a movement, and its progress can be
measured by the increase of declination on the east of it, and its
decrease on the west. And the effect of it on climate is unquestionable.
In all probability it has had an influence upon ours; and a removal of
that area and pole still further west--60 deg. or 80 deg.--would change the
location of the concentrated trade, and the Gulf Stream, and restore to
Greenland the fertility she once had, and which the Faroe Islands now
enjoy. And, on the other hand, its removal as far east of its present
position would again depopulate Greenland, and render it again
inaccessible. But I can not pursue this subject.

Finally, assistance may be derived from the occasional, although
imperfect, accounts of the state of the weather elsewhere, which the
newspapers afford. I have been much indebted to the Associated Press of
New York for intelligence contained in their telegraphic reports.
Occasionally they have been very full and instructive.

On this point, however, there is less of reality in the present than of
hope in the future. The time must come when the collection and
dissemination of meteorological truth, will be deemed an object of
national importance, and national duty. Population is increasing, by
immigration and propagation, in a rapidly progressive ratio. There has
been great danger that it would outrun agricultural production. A short
crop this year would have been disastrous to our prosperity--and the
danger was imminent. Every description of business, and every financial
circle, felt that fever of anxiety it was so well calculated to induce.
The importance of extended agricultural production, and the dependenc