as her wrecking ability was concerned. By means of a trap door in
the diving compartment through the bottom of the boat a man fitted with
a diving-suit could go out and explore a wreck or examine the bottom
almost as easily as a man goes out of his front door to call for an
"extra." It will be thought at once, "But the water will rush in when
the trap door is opened." This is prevented by filling the diving
compartment, which is separated from the main part of the ship by steel
walls, with compressed air of sufficient pressure to keep the water from
coming in--that is, the pressure of water from without equals the
pressure of air from within and neither element can pass into the
other's domain.

An air-lock separates the diver's section from the main hold so that it
is possible to pass from one to the other while the entrance to the sea
is still open. A person entering the lock from the large room first
closes the door between and then gradually admits the compressed air
until the pressure is the same as in the diving compartment, when the
door into it may be safely opened. When returning, this operation is
simply reversed. The lookout stands forward of the diver's space. When
the _Argonaut_ rolls along the bottom, round openings protected with
heavy glass permit the lookout to follow the beam of light thrown by the
searchlight and see dimly any sizable obstruction. When the diving
compartment is in use the man on lookout duty uses a portable telephone
to tell his shipmates in the main room what is happening out in the wet,
and by the same means the reports of the diver can be communicated
without opening the air-lock.

This little ship (thirty-six feet long) has done wonderful things. She
has cruised over the bottom of Chesapeake Bay, New York Bay, Hampton
Roads, and the Atlantic Ocean, her driving-wheels propelling her when
the bottom was hard, and her screw when the oozy condition of the
submarine road made her spiked wheels useless except to steer with. Her
passengers have been able to examine the bottom under twenty feet of
water (without wetting their feet), through the trap door, with the aid
of an electric light let down into the clear depths. Telephone messages
have been sent from the bottom of Baltimore Harbour to the top of the
New York _World_ building, telling of the conditions there in contrast
to the New York editor's aerial perch. Cables have been picked up and
examined without dredging--a hook lowered