As we draw nearer, I attentively examine Back Cup.  Not one of its former inhabitants has been induced to return, and, as it is absolutely deserted, I cannot imagine why the schooner should visit the place.

Perhaps, however, the Count d’Artigas and his companions have no intention of landing there.  Even though the Ebba should find temporary shelter between the rocky sides of a narrow creek there is nothing to give ground to the supposition that a wealthy yachtsman would have the remotest idea of fixing upon as his residence an arid cone exposed to all the terrible tempests of the Western Atlantic.  To live hero is all very well for rustic fishermen, but not for the Count d’Artigas, Engineer Serko, Captain Spade and his crew.

Back Cup is now only half a mile off, and the seaweed thrown up on its rocky base is plainly discernible.  The only living things upon it are the sea-gulls and other birds that circle in clouds around the smoking crater.

When she is only two cable’s lengths off, the schooner slackens speed, and then stops at the entrance of a sort of natural canal formed by a couple of reefs that barely rise above the water.

I wonder whether the Ebba will venture to try the dangerous feat of passing through it.  I do not think so.  She will probably lay where she is—­though why she should do so I do not know—­for a few hours, and then continue her voyage towards the east.

However this may be I see no preparations in progress for dropping anchor.  The anchors are suspended in their usual places, the cables have not been cleared, and no motion has been made to lower a single boat.

At this moment Count d’Artigas, Engineer Serko and Captain Spade go forward and perform some manoeuvre that is inexplicable to me.

I walk along the port side of the deck until I am near the foremast, and then I can see a small buoy that the sailors are hoisting in.  Almost immediately the water, at the same spot becomes dark and I observe a black mass rising to the surface.  Is it a big whale rising for air, and is the Ebba in danger of being shattered by a blow from the monster’s tail?

Now I understand!  At last the mystery is solved.  I know what was the motor that caused the schooner to go at such an extraordinary speed without sails and without a screw.  Her indefatigable motor is emerging from the sea, after having towed her from the coast of America to the archipelago of the Bermudas.  There it is, floating alongside—­a submersible boat, a submarine tug, worked by a screw set in motion by the current from a battery of accumulators or powerful electric piles.

On the upper part of the long cigar-shaped iron tug is a platform in the middle of which is the “lid” by which an entrance is effected.  In the fore part of the platform projects a periscope, or lookout, formed by port-holes or lenses through which an electric searchlight can throw its gleam for some distance under water in front of and on each side of the tug.  Now relieved of its ballast of water the boat has risen to the surface.  Its lid will open and fresh air will penetrate it to every part.  In all probability, if it remained submerged during the day it rose at night and towed the Ebba on the surface.