The only difficulty in proceeding lay in not sliding too fast down an incline of about forty-five degrees; happily certain asperities and a few blisterings here and there formed steps, and we descended, letting our baggage slip before us from the end of a long rope.
But that which formed steps under our feet became stalactites overhead. The lava, which was porous in many places, had formed a surface covered with small rounded blisters; crystals of opaque quartz, set with limpid tears of glass, and hanging like clustered chandeliers from the vaulted roof, seemed as it were to kindle and form a sudden illumination as we passed on our way. It seemed as if the genii of the depths were lighting up their palace to receive their terrestrial guests.
“It is magnificent!” I cried spontaneously. “My uncle, what a sight! Don’t you admire those blending hues of lava, passing from reddish brown to bright yellow by imperceptible shades? And these crystals are just like globes of light.”
“Aye, you think so, do you, Axel, my boy? Well, you will see greater splendours than these, I hope. Now let us march: march!”
He had better have said slide, for we did nothing but drop down the steep inclines. It was the facilis descensus Averni of Virgil. The compass, which I consulted frequently, gave our direction as southeast with inflexible steadiness. This lava stream deviated neither to the right nor to the left.
Yet there was no sensible increase of temperature. This justified Davy’s theory, and more than once I consulted the thermometer with surprise. Two hours after our departure it only marked 10° (50° Fahr. ), an increase of only 4°. This gave reason for believing that our descent was more horizontal than vertical. As for the exact depth reached, it was very easy to ascertain that; the Professor measured accurately the angles of deviation and inclination on the road, but he kept the results to himself.