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.

But if the mechanical power of the tug is produced by electricity the latter must be furnished by some manufactory where it is stored, and the means of procuring the batteries is not to be found on Back Cup, I suppose.

And then, why does the _Ebba_ have recourse to this submarine towing system? Why is she not provided with her own means of propulsion, like other pleasure-boats?

These are things, however, upon which I have at present no leisure to ruminate.

The lid of the tug opens and several men issue on to the platform. They are the crew of this submarine boat, and Captain Spade has been able to communicate with them and transmit his orders as to the direction to be taken by means of electric signals connected with the tug by a wire that passes along the stem of the schooner.

Engineer Serko approaches me and says, pointing to the boat:

"Get in."

"Get in!" I exclaim.

"Yes, in the tug, and look sharp about it."

As usual there is nothing for it but to obey. I hasten to comply with the order and clamber over the side.

At the same time Thomas Roch appears on deck accompanied by one of the crew. He appears to be very calm, and very indifferent too, and makes no resistance when he is lifted over and lowered into the tug. When he has been taken in, Count d'Artigas and Engineer Serko follow.

Captain Spade and the crew of the _Ebba_ remain behind, with the exception of four men who man the dinghy, which has been lowered. They have hold of a long hawser, with which the schooner is probably to be towed through the reef. Is there then a creek in the middle of the rocks where the vessel is secure from the breakers? Is this the port to which she belongs?

They row off with the hawser and make the end fast to a ring in the reef.