attained.

The direct action of the sun's rays upon the earth, particularly those
portions which lie north and south of the tropics, is not the only source
from which the supply of heat is derived. Although there is a general
increase of heat in spring and summer when the sun travels north, and of
cold when he travels south in winter, yet there are frequent
irregularities attending both. Very sudden and great changes occur in each
of them. Frost sometimes, cool weather often, occurs in midsummer, and
considerable heat and tornadoes in midwinter. And ordinarily the maxima
and minima of each month and, indeed, of each week are widely apart. Even
in the polar regions, in midwinter, _where the sun does not shine at all_,
the same moderating changes with which we are conversant occur in degree.
An extract or two from the register found in Dr. Kane's narrative of the
"Grinnell Expedition" will illustrate this.

JANUARY 1851, (LATITUDE ABOUT 74 deg., LONGITUDE ABOUT 70 deg.).

Date. Wind. Force. Ther. Bar. Sky and Weather.

Jan. 3 calm -26.1 29.62 blue sky, m.
" 4 W. gent breeze -21.3 29.53 blue sky,
detached clouds, m.
" 5 W. by N. gent breeze -3.9 29.59 blue sky, m.,
clouded over.
" 6 W. by S. light breeze -0.8 29.67 clouded over, m.,
snow.
" 7 W. gent breeze -14.4 29.96 blue sky, detached
clouds, m.
" 8 W.S.W. light air -21.2 30.14 blue sky, m.
" 29 W.N.W. light air -18.9 30.19 blue sky.
" 30 NW. by W. light air -13.5 30.17 clouded over, m.
" 31 NW. by W. gent breeze -4.4 29.35 clouded over, snow.
Feb. 1 W. light breeze -11.7 29.27 cloudy, blue sky, m.
" 2 W. light air -25.1 29.62 blue sky, detached
clouds, m.

These extracts are instructive. It will be seen that on the 3d of
January, when the sun had been absent some weeks, it was calm, the
thermometer stood at 26 deg. below zero (the - or minus mark before the
figures indicates that), and the barometer at 29.62, with blue sky,
somewhat misty or hazy--(the letter "m." standing for misty or hazy)--a
state of the air which existed most of the time when it did no