“IT is not late yet, Uncle,” said Jules; “you ought to tell us about those terrible mountains, those volcanoes that the showers of ashes come from.”

At the word “volcano,” Emile, who was already asleep, rubbed his eyes and became all attention. He too wanted to hear the great story. As usual, their uncle yielded to their entreaties.

“A volcano is a mountain that throws up smoke, calcined dust, red-hot stones, and melted matter called lava. The summit is hollowed out in a great excavation having the shape of a funnel, sometimes several leagues in circumference. That is what we call the crater. The bottom of the crater communicates with a tortuous conduit or chimney too deep to estimate. The principal volcanoes of Europe are: Vesuvius, near Naples; Etna in Sicily; Hecla in Iceland. Most of the time a volcano is either in repose or throwing up a simple plume of smoke; but from time to time, with intervals that may be very long, the mountain grumbles, trembles, and vomits torrents of fiery substances. It is then said to be in eruption. To give you a general idea of the most remarkable phenomena attending volcanic eruption, I will choose Vesuvius, the best known of the European volcanoes.

“An eruption is generally announced beforehand by a column of smoke that fills the orifice of the crater and rises vertically, when the air is calm, to nearly a mile in height. At this elevation it spreads out in a sort of blanket that intercepts the sun’s rays. Some days before the eruption the column of smoke sinks down on the volcano, covering it with a big black cloud. Then the earth begins to tremble around Vesuvius; rumbling detonations under the ground are heard, louder and louder each moment, soon exceeding in intensity the most violent claps of thunder. You would think you heard the cannonades of a numerous artillery detonating ceaselessly in the mountain’s sides.

“All at once a sheaf of fire bursts from the crater to the height of 2000 or 3000 meters. The cloud that is floating over the volcano is illumined by the redness of the fire; the sky seems inflamed. Millions of sparks dart out like lightning to the top of the blazing sheaf, describe great arcs, leaving on their way dazzling trails, and fall in a shower of fire on the slopes of the volcano. These sparks, so small from a distance, are incandescent masses of stone, sometimes several meters in dimension, and of a sufficient momentum to crush the most solid build............