Year: 1874




The arrival of the comet at its perihelion on
the 9th inst gives new turn to its history,
which will be steadfastly watched by its many
ardent admirers. The great meteor is now
about one-third nearer the sun than we are, or
aboutsixty millions of miles from the fiery orb.
The effect OF this approach to the sun is neces-
sarily great in the analysis of the cometic mat
ter by solar heat and the vaporizahon of the
meteor. In this relation our article published
elsewhere to-day will have a general interest.


The only explanation that has been given
for the apparent contraction Of comets as
they are perihelioned is that they are partly
evaporated by the heat and the cosmical
cloud is converted into invisible cometary
mist The whole mass Of Halley's comet, in
1856, was thus converted into invisible
gas, and afterwards, on cooling, was con-
densed so as to become again apparent. The
change which the great comets undergo from
their near advance toward the sun is one of
the most interesting points Of investigation
in terrestrial physics; for from what
we know of the powerful agency of
aqueous vapor on our planet we may
not unphilosophically conclude that the
cometary vapor, expanding over millions of
miles in space, plays for the time being an
important part in the distribution Of solar
heat through the solar system. Every one
has observed on an intensely hot midsummer
day what boon small feecy cloud flying
overhead is to the pedestrian in screening him
from the rays above. If condensed such
cloud would probably not furnish water
enough to moisten handkerchief, but the
vaporous particles are potential in arresting
the down-pouring food of solar radiation
We know that the water of the tropi-
cal ocean, when converted into invisible
vapor, occupies between sixteen and seve.teen
hundred times its original volume. This
is, however, only under an equatorial tenn
perature of from eighty-fve degrees to ninety
five degrees Fahrenheit-a very low tempera-
ture, comparatively. But in the vaporization
Of comets when at the perihelion tempera-
ture ranging from five thousand to twenty
five thousand times that of an equatorial sun,
is brought to bear upon the cometary matter.


The inconceivable attenuation and expan-
sion due to such thermometric extremes can
be family indicated only by immense COM
etary clouds, stretching over many millions
of miles in interplanetary space and serving
to divert or retard or stop the tides of solar
heat It would, therefore, not appear re-
markable should accurate research hereafter
prove that comets have an important inf1u-
ence on the climate and weather of the season
Such has been the worlds belief for
ages, and though modern science, with its
iconoclastic tendencies to sweep away all that
is old, may rejec. the thought maturer re-
suits may confirm it.


Should the perihelioned comet of 1874
exert this influence, as some think it has done
already, the effect will be most marked, per-
haps, in reducing the July thermometric mean.
The comet of Coggia will, now that it has
made its closest approach to the sun, rapidly
pay its respects to us. According to the
reliable computation Of Astronomer Hind
the great meteor will be nearest the earth on
the night of July %. 1t will then be less
than one-third Of our distance from the sun, or
within thirty millions of miles of our globe.