_THERMOMETRIC STATION ON MONT BLANC._
The thermometers referred to at p. 17 were placed on Mont Blanc in
1859. I had proposed to the Royal Society some time previously to
establish a series of stations between the top and bottom of the
mountain, and the council of the society was kind enough to give me
its countenance and aid in the undertaking. At Chamouni I had a number
of wooden piles shod with iron. The one intended for the summit was
twelve feet long and three inches square; the others, each ten feet
long, were intended for five stations between the top of the mountain
and the bottom of the Glacier de Bossons. Each post was furnished with
a small cross-piece, to which a horizontal minimum thermometer might
be attached. Six-and-twenty porters were found necessary to carry
all the apparatus to the Grands Mulets, whence fourteen of them were
immediately sent back. The other twelve, with one exception, reached
the summit, whence six of them were sent back. Six therefore remained.
In addition to these we had three guides, Auguste Balmat being the
principal one; these, with Dr. Frankland and myself, made up eleven
persons in all. Though the main object of the expedition was to plant
the posts and fix the thermometers, I was very anxious to make some
observations on the transparency of the lower strata of the atmosphere
to the solar heat-rays. I therefore arranged a series of observations
with the Abbé Veuillet, of Chamouni; he was to operate in the valley,
while I observed at the top. Our instruments were of the same kind;
in this way I hoped to determine the influence of the stratum of air
interposed between the top and bottom of the mountain upon the solar
radiation.
Wishing to commence the observations at daybreak, I had a tent carried
to the summit, where I proposed to spend the night. The tent was ten
feet in diameter, and into it the whole eleven of us were packed. The
north wind blew rather fiercely over the summit, but we dropped down
a few yards to leeward, and thus found shelter. Throughout the night
we did not suffer at all from cold, though we had no fire, and the
adjacent snow was 15° Cent., or 27° Fahr., below the freezing point of
water. We were all however indisposed. I was indeed very unwell when I
quitted Chamouni; but had I faltered my party would have melted away. I
had frequently cast off illness on previous occasions, and hoped to do
so now. But in this I was unsuccessful; my illness was more deep-rooted
than ordinary, and it augmented during the entire period of the ascent.
Towards morning, however, I became stronger, while with some of my
companions the reverse was the case. At daybreak the wind increased in
force, and as the fine snow was perfectly dry, it was driven over us
in clouds. Had no other obstacle existed, this alone would have been
sufficient to render the observations on solar radiation impossible.
We were therefore obliged to limit ourselves to the principal object
of the expedition--the erection of the post for the thermometers.
It was sunk six feet in the snow, while the remaining six feet were
exposed to the air. A minimum thermometer was screwed firmly on to the
cross-piece of the post; a maximum thermometer was screwed on beneath
this, and under this again a wet and dry bulb thermometer. Two minimum
thermometers were also placed in the snow--one at a depth of six,
and the other at a depth of four feet below the surface--these being
intended to give some information as to the depth to which the winter
cold penetrates. At each of the other stations we placed a minimum
thermometer in the ice or snow, and a maximum and a minimum in the air.
The stations were as follows:--The summit, the Corridor, the Grand
Plateau, the glacier near the Grands Mulets, and two additional ones
between the Grands Mulets and the end of the Glacier de Bossons. We
took up some rockets, to see whether the ascensional power, or the
combustion, was affected by the rarity of the air. During the night,
however, we were enveloped in a dense mist, which defeated our purpose.
One rocket was sent up which (though we did not know it) penetrated the
mist, and was seen at Chamouni. Lecomte’s experiments on the alleged
influence of light and rarefaction in retarding combustion caused me to
resolve on making a series of experiments on Mont Blanc. Dr. Frankland
was kind enough to undertake their execution. Six candles were chosen
at Chamouni, and carefully weighed. All of them were permitted to
burn for one hour at the top, and were again weighed when we returned
to Chamouni. They were afterwards permitted to burn an hour below.
Rejecting one candle, which gave a somewhat anomalous result, we found
that the quantity consumed above was, within the limits of error, the
same as that consumed at the bottom. This result surprised us all
the more, inasmuch as the _light_ of the candles appeared to be much
feebler at the top than at the bottom of the mountain.
The explosion of a pistol was sensibly weaker at the top than at a
low level. The _shortness_ of the sound was remarkable; but it bore no
resemblance to the sound of a cracker, to which in acoustic treatises
it is usually compared. It resembled more the sound produced by the
expulsion of a cork from a champagne-bottle, but it was much louder.
The sunrise from the summit was singularly magnificent. The snow on the
shaded flanks of the mountain was of a pure blue, being illuminated
solely by the _reflected_ light of the sky; the summit of the mountain,
on the contrary, was crimson, being illuminated by _transmitted_ light.
The contrast of both was finer than I can describe.
About twenty hours were spent upon the top of Mont Blanc on this
occasion. Had I been better satisfied with the conduct of the guides,
it would have given me pleasure at the time to dwell upon this
out-of-the-way episode in mountain life. But a temper, new to me, and
which I thought looked very like mutiny, showed itself on the part
of some of my men. Its manifestation was slight, I must say, in most
cases, and conspicuous only in one. Regrets and apologies followed,
and due allowance ought to be made for the perfectly novel position in
which the men found themselves. The awe of entire strangeness is very
powerful in some minds; and to my companions the notion of spending
a night at the top of Mont Blanc was passing strange. The thing had
never been attempted previously, nor has the experiment been repeated
since.
As stated at p. 17, I made an attempt during the execrable weather
of 1860 to reach the top, but was driven down after a delay of
twenty hours at the Grands Mulets. The same weather destroyed the
lower stations. In 1861, though the cross still remained at the top,
the thermometers exhibited broken columns and were worthless for
observation.
I may add, in conclusion, that the lowest temperature at the summit of
the Jardin during the winter of 1858 was 21° Cent. below zero. In 1859
I vainly endeavoured to find a thermometer which had been placed in the
snow upon the summit of Mont Blanc a year previously.