BEFORE turning into "their nest," as Paganel had called it, he,
and Robert, and Glenarvan climbed up into the observatory to have
one more inspection of the liquid plain.  It was about nine o'clock;
the sun had just sunk behind the glowing mists of the western horizon.
The eastern horizon was gradually assuming a most stormy aspect.
A thick dark bar of cloud was rising higher and higher, and by degrees
extinguishing the stars.  Before long half the sky was overspread.
Evidently motive power lay in the cloud itself, for there was
not a breath of wind.  Absolute calm reigned in the atmosphere;
not a leaf stirred on the tree, not a ripple disturbed the surface
of the water.  There seemed to be scarcely any air even,
as though some vast pneumatic machine had rarefied it.
The entire atmosphere was charged to the utmost with electricity,
the presence of which sent a thrill through the whole nervous
system of all animated beings.
"We are going to have a storm," said Paganel.
"You're not afraid of thunder, are you, Robert?" asked Glenarvan.
"No, my Lord!" exclaimed Robert.  "Well, my boy, so much the better,
for a storm is not far off."
"And a violent one, too," added Paganel, "if I may judge
by the look of things."
"It is not the storm I care about," said Glenarvan,
"so much as the torrents of rain that will accompany it.
We shall be soaked to the skin.  Whatever you may say, Paganel,
a nest won't do for a man, and you will learn that soon,
to your cost."
"With the help of philosophy, it will," replied Paganel.
"Philosophy! that won't keep you from getting drenched."
"No, but it will warm you."
"Well," said Glenarvan, "we had better go down to our friends,
and advise them to wrap themselves up in their philosophy and their
ponchos as tightly as possible, and above all, to lay in a stock
of patience, for we shall need it before very long."
Glenarvan gave a last glance at the angry sky.  The clouds now covered
it entirely; only a dim streak of light shone faintly in the west.
A dark shadow lay on the water, and it could hardly be distinguished from
the thick vapors above it.  There was no sensation of light or sound.
All was darkness and silence around.
"Let us go down," said Glenarvan; "the thunder will soon burst over us."
On returning to the bottom of the tree, they found themselves,
to their great surprise, in a sort of dim twilight, produced by
myriads of luminous specks which appeared buzzing confusedly
over the surface of the water.
"It is phosphorescence, I suppose," said Glenarvan.
"No, but phosphorescent insects, positive glow-worms, living diamonds,
which the ladies of Buenos Ayres convert into magnificent ornaments."
"What!" exclaimed Robert, "those sparks flying about are insects!"
"Yes, my boy."
Robert caught one in his hand, and found Paganel was right.
It was a kind of large drone, an inch long, and the Indians
call it "tuco-tuco." This curious specimen of the COLEOPTERA
sheds its radiance from two spots in the front of its
breast-plate, and the light is sufficient to read by.
Holding his watch close to the insect, Paganel saw distinctly
that the time was 10 P. M.
On rejoining the Major and his three sailors, Glenarvan warned
them of the approaching storm, and advised them to secure
themselves in their beds of branches as firmly as possible,
for there was no doubt that after the first clap of thunder the wind
would become unchained, and the OMBU would be violently shaken.
Though they could not defend themselves from the waters above,
they might at least keep out of the rushing current beneath.
They wished one another "good-night," though hardly daring to hope for it,
and then each one rolled himself in his poncho and lay down to sleep.
But the approach of the great phenomena of nature excites
vague uneasiness in the heart of every sentient being,
even in the most strong-minded. The whole party in the OMBU
felt agitated and oppressed, and not one of them could close
his eyes.  The first peal of thunder found them wide awake.
It occurred about 11 P. M., and sounded like a distant rolling.
Glenarvan ventured to creep out of the sheltering foliage,
and made his way to the extremity of the horizontal branch
to take a look round.
The deep blackness of the night was already scarified with sharp bright
lines, which were reflected back by the water with unerring exactness.
The clouds had rent in many parts, but noiselessly, like some soft
cotton material.  After attentively observing both the zenith and horizon,
Glenarvan went back to the center of the trunk.
"Well, Glenarvan, what's your report?" asked Paganel.
"I say it is beginning in good earnest, and if it goes on so we
shall have a terrible storm."
"So much the better," replied the enthusiastic Paganel; "I should
like a grand exhibition, since we can't run away."
"That's another of your theories," said the Major.
"And one of my best, McNabbs.  I am of Glenarvan's opinion,
that the storm will be superb.  Just a minute ago, when I
was trying to sleep, several facts occurred to my memory,
that make me hope it will, for we are in the region of great
electrical tempests.  For instance, I have read somewhere,
that in 1793, in this very province of Buenos Ayres,
lightning struck thirty-seven times during one single storm.
My colleague, M. Martin de Moussy, counted fifty-five minutes
of uninterrupted rolling."
"Watch in hand?" asked the Major.
"Watch in hand.  Only one thing makes me uneasy," added Paganel,
"if it is any use to be uneasy, and that is, that the culminating
point of this plain, is just this very OMBU where we are.
A lightning conductor would be very serviceable to us at present.
For it is this tree especially, among all that grow in the Pampas,
that the thunder has a particular affection for.  Besides, I need
not tell you, friend, that learned men tell us never to take refuge
under trees during a storm."
"Most seasonable advice, certainly, in our circumstances,"
said the Major.
"I must confess, Paganel," replied Glenarvan, "that you might
have chosen a better time for this reassuring information."
"Bah!" replied Paganel, "all times are good for getting information.
Ha! now it's beginning."
Louder peals of thunder interrupted this inopportune conversation,
the violence increasing with the noise till the whole atmosphere
seemed to vibrate with rapid oscillations.
The incessant flashes of lightning took various forms.
Some darted down perpendicularly from the sky five or six
times in the same place in succession.  Others would have
excited the interest of a SAVANT to the highest degree,
for though Arago, in his curious statistics, only cites two examples
of forked lightning, it was visible here hundreds of times.
Some of the flashes branched out in a thousand different directions,
making coralliform zigzags, and threw out wonderful jets
of arborescent light.
Soon the whole sky from east to north seemed supported by a phosphoric
band of intense brilliancy.  This kept increasing by degrees till it
overspread the entire horizon, kindling the clouds which were faithfully
mirrored in the waters as if they were masses of combustible material,
beneath, and presented the appearance of an immense globe of fire,
the center of which was the OMBU.
Glenarvan and his companions gazed silently at this terrifying spectacle.
They could not make their voices heard, but the sheets of white light
which enwrapped them every now and then, revealed the face of one and
another, sometimes the calm features of the Major, sometimes the eager,
curious glance of Paganel, or the energetic face of Glenarvan,
and at others, the scared eyes of the terrified Robert, and the careless
looks of the sailors, investing them with a weird, spectral aspect.
However, as yet, no rain had fallen, and the wind had not risen in
the least.  But this state of things was of short duration; before long
the cataracts of the sky burst forth, and came down in vertical streams.
As the large drops fell splashing into the lake, fiery sparks seemed
to fly out from the illuminated surface.
Was the rain the FINALE of the storm?  If so, Glenarvan and his
companions would escape scot free, except for a few vigorous
douche baths.  No. At the very height of this struggle of the
electric forces of the atmosphere, a large ball of fire appeared
suddenly at the extremity of the horizontal parent branch,
as thick as a man's wrist, and surrounded with black smoke.
This ball, after turning round and round for a few seconds,
burst like a bombshell, and with so much noise that the explosion
was distinctly audible above the general FRACAS.  A sulphurous
smoke filled the air, and complete silence reigned till the voice
of Tom Austin was heard shouting:
"The tree is on fire."
Tom was right.  In a moment, as if some fireworks were being ignited,
the flame ran along the west side of the OMBU; the dead wood and nests
of dried grass, and the whole sap, which was of a spongy texture,
supplied food for its devouring activity.
The wind had risen now and fanned the flame.  It was time to flee,
and Glenarvan and his party hurried away to the eastern side
of their refuge, which was meantime untouched by the fire.
They were all silent, troubled, and terrified, as they watched
branch after branch shrivel, and crack, and writhe in the flame like
living serpents, and then drop into the swollen torrent, still red
and gleaming, as it was borne swiftly along on the rapid current.
The flames sometimes rose to a prodigious height, and seemed almost
lost in the atmosphere, and sometimes, beaten down by the hurricane,
closely enveloped the OMBU like a robe of Nessus.  Terror seized
the entire group.  They were almost suffocated with smoke,
and scorched with the unbearable heat, for the conflagration
had already reached the lower branches on their side of
the OMBU.  To extinguish it or check its progress was impossible;
and they saw themselves irrevocably condemned to a torturing death,
like the victims of Hindoo divinities.
At last, their situation was absolutely intolerable.
Of the two deaths staring them in the face, they had better
choose the less cruel.
"To the water!" exclaimed Glenarvan.
Wilson, who was nearest the flames, had already plunged into the lake,
but next minute he screamed out in the most violent terror:
"Help!  Help!"
Austin rushed toward him, and with the assistance of the Major,
dragged him up again on the tree.
"What's the matter?" they asked.
"Alligators! alligators!" replied Wilson.
The whole foot of the tree appeared to be surrounded by these
formidable animals of the Saurian order.  By the glare of the flames,
they were immediately recognized by Paganel, as the ferocious species
peculiar to America, called CAIMANS in the Spanish territories.
About ten of them were there, lashing the water with their powerful tails,
and attacking the OMBU with the long teeth of their lower jaw.
At this sight the unfortunate men gave themselves up to be lost.
A frightful death was in store for them, since they must either
be devoured by the fire or by the caimans.  Even the Major said,
in a calm voice:
"This is the beginning of the end, now."
There are circumstances in which men are powerless, when the
unchained elements can only be combated by other elements.
Glenarvan gazed with haggard looks at the fire and water leagued
against him, hardly knowing what deliverance to implore from Heaven.
The violence of the storm had abated, but it had developed
in the atmosphere a considerable quantity of vapors,
to which electricity was about to communicate immense force.
An enormous water-spout was gradually forming in the south--
a cone of thick mists, but with the point at the bottom,
and base at the top, linking together the turbulent water
and the angry clouds.  This meteor soon began to move forward,
turning over and over on itself with dizzy rapidity,
and sweeping up into its center a column of water from the lake,
while its gyratory motions made all the surrounding currents
of air rush toward it.
A few seconds more, and the gigantic water-spout threw itself on the OMBU,
and caught it up in its whirl.  The tree shook to its roots.
Glenarvan could fancy the caimans' teeth were tearing it up from the soil;
for as he and his companions held on, each clinging firmly to the other,
they felt the towering OMBU give way, and the next minute it fell right
over with a terrible hissing noise, as the flaming branches touched
the foaming water.
It was the work of an instant.  Already the water-spout
had passed, to carry on its destructive work elsewhere.
It seemed to empty the lake in its passage, by continually
drawing up the water into itself.
The OMBU now began to drift rapidly along, impelled by wind
and current.  All the caimans had taken their departure,
except one that was crawling over the upturned roots,
and coming toward the poor refugees with wide open jaws.
But Mulrady, seizing hold of a branch that was half-burned off,
struck the monster such a tremendous blow, that it fell back
into the torrent and disappeared, lashing the water with
its formidable tail.
Glenarvan and his companions being thus delivered from the
voracious SAURIANS, stationed themselves on the branches windward
of the conflagration, while the OMBU sailed along like a blazing
fire-ship through the dark night, the flames spreading themselves
round like sails before the breath of the hurricane.