At last the grappling-chains, air-chambers, and automatic grappling-irons were embarked on board the Susquehanna.  J.T.  Maston, the engineer Murchison, and the Gun Club delegates already occupied their cabins.  There was nothing to do but to start.

On the 21st of December, at 8 p.m., the corvette set sail on a calm sea with a rather cold north-east wind blowing.  All the population of San Francisco crowded on to the quays, mute and anxious, reserving its hurrahs for the return.

The steam was put on to its maximum of tension, and the screw of the Susquehanna carried it rapidly out of the bay.

It would be useless to relate the conversations on board amongst the officers, sailors, and passengers.  All these men had but one thought.  Their hearts all beat with the same emotion.  What were Barbicane and his companions doing whilst they were hastening to their succour?  What had become of them?  Had they been able to attempt some audacious manoeuvre to recover their liberty?  No one could say.  The truth is that any attempt would have failed.  Sunk to nearly two leagues under the ocean, their metal prison would defy any effort of its prisoners.

On the 23rd of December, at 8 a.m., after a rapid passage, the Susquehanna ought to be on the scene of the disaster.  They were obliged to wait till twelve o’clock to take their exact bearings.  The buoy fastened on to the sounding-line had not yet been seen.

At noon Captain Blomsberry, helped by his officers, who controlled the observation, made his point in presence of the delegates of the Gun Club.  That was an anxious moment.  The Susquehanna was found to be at some minutes west of the very spot where the projectile had disappeared under the waves.

The direction of the corvette was therefore given in view of reaching the precise spot.

At 12.47 p.m. the buoy was sighted.  It was in perfect order, and did not seem to have drifted far.

“At last!” exclaimed J.T.  Maston.

“Shall we begin?” asked Captain Blomsberry.

“Without losing a second,” answered J.T.  Maston.

Every precaution was taken to keep the corvette perfectly motionless.

Before trying to grapple the projectile, the engineer, Murchison, wished to find out its exact position on the sea-bottom.  The submarine apparatus destined for this search received their provision of air.  The handling of these engines is not without danger, for at 20,000 feet below the surface of the water and under such great pressure they are exposed to ruptures the consequences of which would be terrible.

J.T.  Maston, the commander’s brother, and the engineer Murchison, without a thought of these dangers, took their places in the air-chambers.  The commander, on his foot-bridge, presided over the operation, ready to stop or haul in his chains at the least signal.  The screw had been taken off, and all the force of the machines upon the windlass would soon have brought up the apparatus on board.