About seven o'clock in the morning I jump out of bed. If I am a prisoner in the cavern I am at least not imprisoned in my grotto cell. The door yields when I turn the handle and push against it, and I walk out.
Thirty yards in front of me is a rocky plane, forming a sort of quay that extends to right and left. Several sailors of the _Ebba_ are engaged in landing bales and stores from the interior of the tug, which lays alongside a little stone jetty.
A dim light to which my eyes soon grow accustomed envelops the cavern and comes from a hole in the centre of the roof, through which the blue sky can be seen.
"It is from that hole that the smoke which can be seen for such a distance issues," I say to myself, and this discovery suggests a whole series of reflections.
Back Cup, then, is not a volcano, as was supposed--as I supposed myself. The flames that were seen a few years ago, and the columns of smoke that still rise were and are produced artificially. The detonations and rumblings that so alarmed the Bermudan fishers were not caused by the internal workings of nature. These various phenomena were fictitious. They manifested themselves at the mere will of the owner of the island, who wanted to scare away the inhabitants who resided on the coast. He succeeded, this Count d'Artigas, and remains the sole and undisputed monarch of the mountain. By exploding gunpowder, and burning seaweed swept up in inexhaustible quantities by the ocean, he has been able to simulate a volcano upon the point of eruption and effectually scare would-be settlers away!
The light becomes stronger as the sun rises higher, the daylight streams through the fictitious crater, and I shall soon be able to estimate the cavern's dimensions. This is how I calculate:
Exteriorly the island of Back Cup, which is as nearly as possible circular, measures two hundred and fifty yards in circumference, and presents an interior superficies of about six acres. The sides of the mountain at its base vary in thickness from thirty to a hundred yards.
It therefore follows that this excavation practically occupies the whole of that part of Back Cup island which appears above water. As to the length of the submarine tunnel by which communication is obtained with the outside, and through which the tug passed, I estimate that it is fifty yards in length.