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purposes to which submarine navigation would be applied in case of war.
In the article Diving Bell, published in 1826, in the ‘Encyclopedia
Metropolitana,’ I gave a {212} description and drawings of an
_open_ submarine vessel which would contain sufficient air for the
consumption of four persons during more than two days. A few years ago,
I understand, experiments were made in the Seine at Paris, on a similar
kind of open diving-vessel. Such a vessel could be propelled by a
screw, and might enter, without being suspected, any harbour, and place
any amount of explosive matter under the bottoms of ships at anchor.

Such means of attack would render even iron and iron-clad ships unsafe
when blockading a port. For though chains were kept constantly passing
under their keels, it would yet be possible to moor explosive magazines
at some distance below, which would effectually destroy them.

{213}




CHAPTER XVI.

EXPERIENCE BY FIRE.


Baked in an Oven — A Living Volcano — Vesuvius in action — Carried up
the Cone of Ashes in a Chair — View of the Crater in a Dark Night —
Sunrise — Descent by Ropes and Rolling into the great Crater — Watched
the small Crater in active eruption at intervals — Measured a Base of
330 feet — Depth of great Crater 570 feet — Descent into small Crater
— A Lake of red-hot Boiling Lava — Regained the great Crater with
the sacrifice of my Boots — Lunched on Biscuits and Irish Whisky —
Visit to the Hot Springs of Ischia — Towns destroyed by Earthquake —
Coronets of Smoke projected by Vesuvius — Artificial Mode of producing
them — Fire-damp visited in Welsh Coal-mine in company with Professor
Moll.


_Baked in an Oven._

Calling one morning upon Chantrey, I met Captain Kater and the late
Sir Thomas Lawrence, the President of the Royal Academy. Chantrey was
engaged at that period in casting a large bronze statue. An oven of
considerable size had been built for the purpose of drying the moulds.
I made several inquiries about it, and Chantrey kindly offered to let
me pay it a visit, and thus ascertain by my own feelings the effects of
high temperature on the human body.

I willingly accepted the proposal, and Captain Kater offered
to accompany me. Sir Thomas Lawrence, who was suffering from
indisposition, did not think it prudent to join our party. In fact, he
died on the second or third day after our experiment.

The iron folding-doors of the small room or oven were {214} opened.
Captain Kater and myself entered, and they were then closed upon
us. The further _corner_ of the room, which was paved with squared
stones, was visibly of a dull-red heat. The thermometer marked, if
I recollect rightly, 265°. The pulse was quickened, and I ought to
have counted but did not count the number of inspirations per minute.
Perspiration commenced immediately and was very copious. We remained,
I believe, about five or six minutes without very great discomfort,
and I experienced no subsequent inconvenience from the result of the
experiment.


_A Living Volcano._

I have never been so fortunate as to be _conscious_ of having
experienced the least shock of an earthquake, although, when a town had
been destroyed in Ischia I hastened on from Rome in the hope of getting
a slight shake. My passion was disappointed, so I consoled myself by a
flirtation with a volcano.

〈VESUVIUS—CORONETS OF SMOKE.〉

The situation of my apartments during my residence at Naples enabled me
constantly to see the cone of Vesuvius, and the continual projections
of matter from its crater. Amongst these were occasionally certain
globes of air, or of some gas, which, being shot upwards to a great
height above the cone, spread out into huge coronets of smoke, having a
singular motion amongst their particles.

A similar phenomenon sometimes occurs on a small scale during the
firing of heavy ordnance. I have frequently seen such at Plymouth and
elsewhere; but I was not satisfied about the cause of this phenomenon.
I was told that it occurred more frequently if the muzzle of the gun
were rubbed with grease; but this did not always succeed.

〈ARTIFICIAL IMITATION.〉

Soon after my return to London I made a kind of drum, by {215}
stretching wet parchment over a large tin funnel. On directing the
point of the funnel at a candle placed a few feet distant, and giving
a smart blow upon the parchment, it is observed that the candle is
immediately extinguished.

This arises from what is called an air shot. In fact, the air in the
tubular part is projected bodily forward, and so blows out the candle.
The statements about persons being killed by cannon balls passing close
to but not touching them, if true, are probably the results of air
shots.

Wishing to trace the motions of such air shots, I added two small tubes
towards the large end of the tin funnel, in order that I might fill it
with smoke, and thus trace more distinctly the progress of the ball of
air.

To my great delight the first blow produced a beautiful coronet of
smoke, exactly resembling, on a small scale, the explosions from cannon
or the still more attractive ones from Vesuvius.

If phosphoretted hydrogen or any other gas, which takes fire in air,
were thus projected upwards, a very singular kind of fire-work would be
produced.

It is possible in dark nights or in fogs that by such means signals
might be made to communicate news or to warn vessels of danger.

Vesuvius was then in a state of moderate activity. It had a huge cone
of ashes on its summit, surrounding an extensive crater of great depth.
In one corner of this was a smaller crater, quite on a diminutive
scale, which from time to time ejected red-hot fragments of lava
occasionally to the height of from a thousand to fifteen hundred feet
above the summit of the mountain.

I had taken apartments in the Chiaja, just opposite the volcano, in
order that I might watch it with a telescope. In fact, {216} as I lay
in my bed I had an excellent view of the mountain. My next step was to
consult with Salvatori, the most experienced of the guides, from whom I
had purchased a good many minerals, as to the possibility of getting a
peep down the volcano’s throat.

〈ASCENT TO CRATER BY NIGHT.〉

Salvatori undertook to report to me from time to time the state of the
mountain, round the base of which I made frequent excursions. After
about a fortnight, the explosions were more regular and uniform, and
Salvatori assured me that all the usual known indications led him to
think that it was a fit time for my expedition. As I wished to see as
much as possible, I made arrangements to economize my strength by using
horses or mules to carry me wherever they could go. Where they could
not carry me, as for instance, up the steep slope of the cone of ashes,
I employed men to convey me in a chair.

By these means, I saw in the afternoon and evening of one day a good
deal of the upper part of the mountain, then took a few hours’ repose
in a hut, and reached the summit of the cone long before sunrise.

It was still almost dark: we stood upon the irregular edge of a vast
gulf spread out below at the depth of about five hundred feet. The
plain at the bottom would have been invisible but for an irregular
network of bright-red cracks spread over the whole of its surface.
Now and then the silence was broken by a rush upwards of a flight of
red-hot scoria from the diminutive crater within the large one. These
missiles, however, although projected high above the summit of the
cone, never extended themselves much beyond the small cavity from which
they issued.

Those who have seen the blood-vessels of their own eye by the aid of
artificial light, will have seen on a small scale a {217} perfect
resemblance of the plain which at that time formed the bottom of the
great crater of Vesuvius.

〈SUNRISE FROM THE SUMMIT.〉

As the morning advanced the light increased, and some time before
sunrise we had completed the tour of the top of the great crater. Then
followed that glorious sight—the sun when seen rising from the top of
some lofty mountain.

I now began to speculate upon the means of getting a nearer view of the
little miniature volcano in action at one corner of the gulf beneath
us. We had brought ropes with us, and I had observed, in our tour round
the crater, every dike of congealed lava by which the massive cone was
split. These presented buttresses with frequent ledges or huge steps
by which I hoped, with the aid of ropes, to descend into the Tartarus
below.

Having consulted with our chief guide Salvatori, I found that he was
unwilling to accompany us, and proposed remaining with the other guides
on the upper edge of the crater. Upon the whole, I was not discontented
with the arrangement, because it left a responsible person to keep the
other guides in order, and also sufficient force to lift us up bodily
by the ropes if that should become necessary.

The abruptness of the rocky buttresses compelled us to use ropes, but
the attempt to traverse the steep inclines of light ashes and of fine
sand would have been more dangerous from the risk of being engulfed in
them.

〈DESCENT INTO THE CRATER.〉

Having well examined the several disadvantages of these rough-hewn
irregular Titanic stairs, I selected one which seemed the most
promising for facilitating our descent into the crater. I was
encumbered with one of Troughton’s heavy barometers, strapped to my
back, looking much like Cupid’s quiver, though probably rather heavier.
In my pocket I had an excellent box sextant, and in a rough kind of
basket {218} two or three thermometers, a measuring tape, and a glass
bottle enclosed in a leather case, commonly called a pocket-pistol,
accompanied by a few biscuits.

We began our descent by the aid of two ropes, each supported above
by two guides. I proceeded, trusting to my rope to step wherever I
could, and then cautiously holding on by the rope to spring down to the
next ledge. In this manner we descended until we arrived at the last
projecting ledge of the dike. Nothing then remained for us but to slide
down a steep and lengthened incline of fine sand. Fortunately, the sand
itself was not very deep, and was supported by some solid material
beneath it. I soon found that it was impossible to stand, so I sat down
upon this moving mass, which evidently intended to accompany us in our
journey. At first, to my great dismay, I was relieved from the care
of my barometer, of which the runaway sand immediately took charge.
I then found myself getting deeper and deeper in the sand, and still
accelerating my downward velocity.

Gravity had at last done its work and became powerless. I soon dug
myself out of my sandy couch, and rushed to my faithful barometer lying
at some distance from me with its head just unburied. Fortunately, it
was uninjured. My companion, with more skill or good fortune, or with
less incumbrances, had safely alighted on the burning plain we now
stood upon.

The area of this plain, for it was perfectly flat, was in shape
somewhat elliptical. The surface consisted of a black scoriacious rock,
reticulated with ditches from one to three feet wide, intersecting each
other in every direction. From some of these, fumes not of the most
agreeable odour were issuing. All those above two feet deep showed
that at that depth below us everything was of a dull-red heat. It was
{219} these ditches with red-hot bottoms which, in the darkness of
the night, had presented the singular spectacle I described as having
witnessed on the evening before.

〈MEASUREMENT OF A BASE.〉

At one extremity of this oval plain there was a small cone, from which
the eruptions before described appeared to issue.

My first step, after examining the few instruments I had brought with
me, was to select a spot upon which to measure a base for ascertaining
the depth of the crater from its upper edge.

Having decided upon my base line, I took with my sextant the angle of
elevation of the rim of the crater above a remarkable spot on a level
with my eye. Then fixing my walking-stick into a little crack in the
scoria, I proceeded to measure with a tape a base line of 340 feet.
Arrived at this point, I again took the angle of elevation of the same
part of the rim from the same remarkable spot on a level with the eye.
Then, by way of verification, I remeasured my base line and found it
only differed from the former measure by somewhat less than one foot.
But my walking-stick, which had not penetrated the crack more than a
few inches, was actually in flames.

Having noted down these facts, including the state of the thermometer
and barometer, in my pocket-book, I took first a survey and then a
tour about my fiery domain. I afterwards found, from the result of
this measurement, that our base line was 570 feet below one of the
lowest points of the edge of the crater. Having collected a few mineral
specimens, I applied myself to observe and register the eruptions of
the little embryo volcano at the further extremity of the elliptical
plain.

〈DESCENT INTO SMALL ACTIVE CRATER.〉

These periodical eruptions interested me very much. I proceeded to
observe and register them, and found they occurred {220} at tolerably
regular intervals. At first, I performed this operation at a respectful
distance and out of the reach of the projected red-hot scoria. But as I
acquired confidence in their general regularity, I approached from time
to time more nearly to the little cone of scoria produced by its own
eruptions.

I now perceived an opening in this little cone close to the
perpendicular rock of the interior of the great crater. I was very
anxious to see real fluid lava; so immediately after an eruption, I
rushed to the opening and thus got within the subsidiary crater. But
my curiosity was not gratified, for I observed, about forty or fifty
feet below me, a huge projecting rock, which being somewhat in advance,
effectively prevented me from seeing the lava lake, if any such
existed. I then retreated to a respectful distance from this infant
volcano to wait for the next explosion.

I continued to note the intervals of time between these jets of red-hot
matter, and found that from ten to fifteen minutes was the range of
the intervals of repose. Having once more reconnoitred the descent
into the little volcano, I seized the opportunity of the termination
of one of the most considerable of its eruptions to run towards the
gap and cautiously to pick my way down to the rock which hid from me,
as I supposed, the liquid lava. I was armed with two phials, one of
common smelling salts, and the other containing a solution of ammonia.
On reaching the rock, I found it projected over a lake which was
really filled by liquid fiery lava. I immediately laid myself down,
and looking over its edge, saw, with great delight, lava actually in a
state of fusion.

〈WAVES IN LAKE OF FLUID LAVA.〉

Presently I observed a small bubble swelling up on the surface of the
fluid lava: it became gradually larger and larger, but did not burst. I
had some vague suspicion that {221} this indicated a coming eruption;
but on looking at my watch, I was assured that only one minute had
elapsed since the termination of the last. I therefore watched its
progress; after a time the bubble slowly subsided without breaking.

I now found the heat of the rock on which I was reposing, and the
radiation from the fluid lava, almost insupportable, whilst the
sulphurous effluvium painfully affected my lungs. On looking around, I
fortunately observed a spot a few feet above me, from which I could,
in a standing position, get a better view of the lake, and perhaps
suffer less inconvenience from its vapours. Having reached this spot,
I continued to observe the slow formation and absorption of these
vesicles of lava. One of them soon appeared. Another soon followed
at a different part of the fiery lake, but, like its predecessor, it
disappeared as quietly.

Another swelling now arose about half way distant from the centre of
the cauldron, which enlarged much beyond its predecessors in point of
size. It attained a diameter of about three feet, and then burst, but
not with any explosion. The waves it propagated in the fiery fluid
passed on to the sides, and were thence reflected back just as would
have happened in a lake of water of the same dimensions.

This phenomenon reappeared several times, some of the bubbles being
considerably larger in size, and making proportionally greater
disturbance in the liquid of this miniature crater. I would gladly have
remained a longer time, but the excessive heat, the noxious vapours,
and the warning of my chronometer forbade it. I climbed back through
the gap by which I had descended, and rushed as fast as I could to a
safe distance from the coming eruption.

I was much exhausted by the heat, although I suffered still greater
inconvenience from the vapours. From my {222} observations of the
eruptions before my descent into this little crater, I had estimated
that I might safely allow myself six minutes, but not more than eight,
if I descended into the crater immediately after an eruption.

If my memory does not fail me, I passed about six minutes in examining
it, and the next explosion occurred ten minutes after the former one.
On my return to Naples I found that a pair of thick boots I had worn on
this expedition were entirely destroyed by the heat, and fell to pieces
in my attempt to take them off.

〈BISCUITS AND WHISKY.〉

On my return from the pit of burning fire, I sat down with my companion
to refresh myself with a few biscuits contained in our basket. Cold
water would have been the most refreshing fluid we could have desired,
but we had none, and my impatient friend cried out, “I wish I had a
glass of whisky!” It immediately occurred to me to feel in my own
basket for a certain glass bottle preserved in a tight leather case,
which fortunately being found, I presented to my astonished friend,
with the remark that it contained half a pint of the finest Irish
whisky. This piece of good luck for my fellow-traveller arose not from
my love but from my dislike of whisky. Shortly before my Italian tour
I had been travelling in the north of Ireland, and having exhausted my
brandy, was unable to replace it by anything but whisky, a drink which
I can only tolerate under very exceptional circumstances.


_Hot Springs._

During my residence at Naples in 1828, the government appointed a
commission of members of the Royal Academy of Naples to visit Ischia
and make a report upon the hot springs in that island. Being a foreign
member of the Academy, they {223} did me the honour of placing my name
upon that commission. The weather was very favourable, the party was
most agreeable, and during three or four days I enjoyed the society
of my colleagues, the delightful scenery, and the highly interesting
natural phenomena of that singular island.

〈HOT SPRINGS OF ISCHIA.〉

None of the hot springs were deep: in several we made excavations
which, in all cases, gave increased heat to the water. In one or two,
I believe if we had excavated to a small depth or bored a few feet, we
might have met with boiling water.

I took the opportunity of this visit to view the devastations made by
the recent earthquake in the small town which had been destroyed.

The greater part of the town consisted of narrow streets formed by
small houses built of squared stone. In some of these streets the
houses on one side were thrown down, whilst those a few feet distant,
on the opposite side, although severely damaged, had their walls left
standing.

The landlord of the hotel at which we took up our quarters assured me
the effects of the recent earthquake were entirely confined to a small
portion of the island which he pointed out from the front of his hotel,
and added that it was scarcely felt in other parts.


_Earthquakes._

At the commencement of this chapter I mentioned that I had never been
_consciously_ sensible of the occurrence of an earthquake. I think
it may perhaps be useful to state that on a recent occasion I really
perceived the effects of an earthquake, although at the time I assigned
them to a different cause.

〈UNCONSCIOUS WITNESS OF EARTHQUAKE.〉

On the 6th of last October, about half-past three, a.m., {224} most of
the inhabitants of London who were awake at that hour perceived several
shocks of an earthquake. I also was awake, although not conscious of
the shocks of an earthquake.

As soon as I read of the event in the morning papers, I was forcibly
struck by its coincidence with my own observations, although I had
attributed to them an entirely different cause. In order to explain
this, it is necessary to premise that I had on a former occasion
instituted some experiments for the purpose of ascertaining how far
off the passing of a cart or carriage would affect the steadiness of
a star observed by reflection. Amongst other methods, I had fixed a
looking-glass of about 12 by 16 inches, by a pair of hinges, to the
front wall of my bedroom. It was usually so placed that, as I lay in
bed, at the distance of about 10 or 12 feet, I could see by reflection
a small gas-light burner, which was placed on my left hand.

By this arrangement any tremors propagated through the earth from
passing carriages would be communicated to the looking-glass by
means of the front wall of the house, which rose about 40 feet from
the surface. The image of the small gas-burner reflected in the
looking-glass would be proportionally disturbed. In this state of
things, at about half-past three o’clock of the morning in question,
I observed the reflected image of the gas-light move downwards and
upwards two or three times. I then listened attentively, expecting to
hear the sound of a distant carriage or cart. Hearing nothing of the
kind, I concluded that the earth wave had travelled beyond the limit of
the sound wave, arising from the carriage which produced it. Presently
the image of the gaslight again vibrated up and down, and then
suddenly fell about four or five inches lower down in the glass, where
it remained fixed for a time. Still thinking the observation of no
consequence, {225} I shut my eyes, and after perhaps another minute,
again saw the image in its lower position. It then rose to its former
position, vibrated, and shortly again descended: it remained down for
some time and then resumed its first position.


_Fire Damp._

An opportunity presented itself several years after my examination
of Vesuvius of witnessing another form under which fire occasionally
exerts its formidable power.

I was visiting a friend[37] at Merthyr Tydfil, who possessed very
extensive coal-mines. I inquired of my host whether any fire-damp
existed in them. On receiving an affirmative answer, I expressed a wish
to become personally acquainted with the miner’s invisible but most
dangerous enemy. Arrangements were therefore made for my visit to the
subterranean world on the following day. Professor Moll of Utrecht, who
was also a guest, expressed a wish to accompany me.

[37] The late Sir John J. Guest, Bart.

The entrance to the mine is situated in the side of a mountain. Its
chief manager conducted our expedition to visit the ‘fire-king.’

We found a coal-waggon drawn by a horse, and filled with clean straw,
standing on the railway which led into the workings.

The manager, Professor Moll, and myself, together with two or three
assistants, with candles, lanterns, and Davy-lamps, got into this
vehicle, which immediately entered the adit of the mine. We advanced at
a good pace, passing at intervals doors which opened on our approach
and then instantly closed. Each door had an attendant boy, whose duty
was confined to the regulation of his own door. {226}

Many were the doors we passed before we arrived at the termination of
the tram-road. After travelling about a mile and a half, our carriage
stopped and we alighted. We now proceeded on foot, each carrying
his own candle, until we reached a kind of chamber where one of our
attendants was left with the candles.

〈DRIVE INTO THE MOUNTAIN.〉

We, each holding a Davy-lamp in our hand, advanced towards a small
opening in the side of this chamber, which was so low that we were
compelled to crawl, one after another, on our hands and knees. A
powerful current of air rushed through this small passage. On reaching
the end of it, we found ourselves in a much larger chamber from which



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