"Well, the _Nautilus_ is nothing more or less than a submarine diving chamber," explained Austin. "It is set on the end of the access tube by means of a huge differential that enables it to work back and forth like a flexible hinge. Under the _Nautilus_ and under the access tube are ballast tanks. You boys who have been in the submarine and the diving business in the Navy know how easily that works. We raise or lower the diving compartment simply by 'trimming,' or blowing the tanks. In case the ballast apparatus gets out of commission, we have the _Nautilus_ suspended on cables. They will bring her up again if she gets stuck down there." "Oh, I commence to see it now," interrupted Jay. "The mother boat, or _Jules Verne_, is like your shoulder. The access tube through which you effect an entrance into the _Nautilus_ is like your arm. The _Nautilus_ is like your hand. You raise or lower at will, and you can put the _Nautilus_ down in the water at a distance equal to the length of the access tube, or arm. Isn't that it?" "Exactly, my boy," countered "Cap" Austin. "And can't you see the advantages of such an equipment? Heretofore, we have had to send you divers down to go groping around over the bottom of the sea after we found our quarry. You had to prod and dig and scratch around to find out the condition of the lost ship, how best she was to be entered, and all that. And by that time, you were pretty well played out and had to stop until you got in good trim again." "To say nothing of the tides and the storms that kept pulling us away from our work," added Dick. "Right you are," continued the captain. "But now all that is done away with. When we come to a wreck now we lower the _Nautilus_; you chaps go down with us and from the ports of the _Nautilus_ we inspect the wreck without one of you having to step a foot on the bottom of the sea. When we have looked her over carefully and are all ready to get down to work, then we can let you out the bottom of the _Nautilus_, instead of sending you over the sides of the _Jules Verne_. What do you think of that? Think of it! You are already down in the sea a hundred feet or more. You are not only conserving your strength, but you are much safer than when out in diving armor floundering around in quest of your prey." "What is the _Nautilus_ like inside, and how does she operate?" Dick, mechanically inclined, was eager to solve the whole of this riddle. "You shall know intimately for yourselves within a very short time," answered his captain. "We are going right aboard now, and as soon as Superintendent "Montey" Brown and a number of officials higher up come along we are going to cast off and go out in the Sound to make our first practical tests." That was good news to the Brighton boys and Larry Seymour. Headed by Captain Austin and followed by their good friend Fismes, they crossed the gangplank and stepped on the deck of the _Jules Verne_.