subject to all these favourable conditions that water is instantly
congealed to.ice ! ” Before going into the other “ conclusions ” drawn
from these truly novel “ top and side vacuum” experiments, I will
briefly state the reason that water solidifies- when the air is pumped
out of a receiver in -which water is contained. Whatever be the
temperature at which a vapour is produced, an absorption of heat
always takes place. If, therefore, a liquid evaporates and does not
receive from without a quantity of heat equal to that which is
expended in producing the vapour, its temperature sinks, and the
cooling is greater in proportion as the evaporation is more rapid.
Leslie succeeded in freezing water by means of rapid evaporation.
Under the receiver of an air-pump is placed a vessel containing strong
sulphuric acid, and above it a thin metal capsule, containing a small
quantity of water. On exhausting the receiver the water begins to
boil, and since the vapours are absorbed by the sulphuric acid as fast
as they are generated, a rapid evaporation is produced, which quickly
effects the freezing of the water.
By means of the rapid evaporation of bisulphide of carbon the
formation of ice may be illustrated without the aid of an air-pump.
A little water is dropped on a board, and a capsule of thin copper foil,
containing bisulphide of carbon, is placed in the water. The evaporation
of the bisulphide is accelerated by means of a pair of bellows,
and, after a few minutes, the water freezes round the capsule,
so that the latter adheres to the wood. In like manner, if water
be placed in a test-tube, which is then dipped in a glass containing
ether, and a current of air be blown through the ether, the cold produced
by the rapid evaporation of the ether very soon freezes the water
in the tube. Such experiments as these, which can, and shall, if
necessary, be multiplied to infinity, show the entire absurdity of talking
of “ the atmosphere, which is the mother of heat, being drawn out,”
or of the “ cold within the vacuum being the same which exists on the
unapproachable mountain heights,” or such kindred nonsense. (By
the way, what is the “ converging power ” of a piece of plate glass 1
I am anxious to be informed.)
•The next point to refute is your correspondent’s assertion that heat
does not pass through a vacuum. Radiant heat is propagated in vacuo
as well as in air. This is demonstrated by the following experiment:—
In the bottom of a glass flask (not a plate-glass one in this case) a
thermometer is fixed in such a manner that its bulb occupies the centre
of the flash. The neck of the flask is carefully narrowed by means of
the blowpipe, and then the apparatus having been suitably attached,
a vacuum is produced in the interior. This being done, the tube is
sealed at the narrow part, and we have an exhausted flask containing
a thermometer. On immersing this apparatus in hot water, or on
bringing near it some red-hot charcoal, the thermometer is at once seen
to rise. This could only arise from radiation through the vacuum in
the interior, for glass is so bad a conductor of heat that the heat could
not travel through the sides of the flask and down the stem of the
thermometer in so short a time. (This may also be considered a proof
that the hypothetical ether is present in a vacuum.)
The “ Constant Reader of Colburn’s New Monthly also ” then goes
on to deny my assertion that Tyndall, in common with many other
observers, has recorded high temperature when at considerable elevations.
The “ C. R. of C. N. M. also ” states that “ the story of Tyndall
is apparently a fiction, and is open and apparent nonsense, which I
feel sure your Professor of Chemistry will be careful not to repeat.”
This is a very indiscreet remark, especially as the “ Constant Reader
of Colburn’s New Monthly ” does not seem to have read anything else
but Colburn’s New Monthly, which, admirable as it is, is not a scientific
work, and is not sufficient to base one’s scientific knowledge upon. I
cannot do better than quote Tyndall himself in refutation of the
accusation that I am an inventor of science facts which never existed.
In Tyndall’s “ Glaciers of the Alps,” during the ascent of “ Monte
Rosa,” over 15,000 feet high, when at an elevation of over 12,000
feet, Tyndall says :—“ There was not a breath of air stirring, and
though we stood ankle-deep ib snow, the heat surpassed anything of
the kind I had ever felt; it was the dead suffocating warmth of an
oven which encompassed us on all sides, and from which there seemed
no escape.” The “ Constant Reader of Colburn’s New Monthly ” also
says that “ Tyndall himself, although he is well known as an Alpine
tourist in search of knowledge, to climb such a height would be quite
beyond his physical endurance.”
I am at a loss to understand why this statement is made, for every
reader of even ordinary literature or of the London Times knows that
Professor Tyndall has been up Mont Blanc (16,000 feet) several times,
both alone and in company with Professor Huxley and Dr. Frankland.
His ascent of the Matterhorn (14,000 feet) is a known fact, and Monte
Rosa’s summit has often been trodden by the Professor. In “ Glaciers
of the Alps,” during an ascent of Mont Blanc, he says:—“ At length
success became certain, and at half-past three p.m. we joined hands on
the top.”
Tyndall, in “ Heat as a Mode of Motion,” quotes the following from