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 fi............