_ meant "All right;" four pulls, "I'm coming up." One pull on
the air-pipe signified "Sufficient air;" two pulls, "More air." (pump
faster.) Four pulls was an alarm, and signified "Haul me up." The
aspect of Rooney Machowl's face when endeavouring to understand
Baldwin's explanation of these signals was a sight worth seeing!

But to return to our diver. On reaching the bottom, Maxwell took a coil
of small line which hung on his left arm, and attached one end of it to
a stone or sinker which kept taut the ladder-line by which he had
descended. This was his clew to guide him back to the ladder. Not only
is the light under water very dim--varying of course, according to
depth, until total darkness ensues--but a diver's vision is much
weakened by the muddy state of the water at river-mouths and in
harbours, so that he is usually obliged to depend more on feeling than
on sight. If he were to leave the foot of his ladder without the
guiding-coil, it would be difficult if not impossible to find it again,
and his only resource would be to signal "Haul me up," which would be
undignified, to say the least of it! By means of this coil he can
wander about at will--within the limits of his air-tube tether of
course,--and be certain to find his way back to the ladder-foot in the
darkest or muddiest water.

Having fastened the line, the diver walked in the direction of the rock
on which he had to operate, dropping gradually the coils of the
guiding-line as he proceeded. His progress was very slow, for water is
a dense medium, and man's form is not well adapted for walking in it--as
every bather knows who has attempted to walk when up to his neck in it.
He soon found the object of his search, and went down on his knees
beside the hole already driven into the rock. Even this process of
going on his knees was not so simple as it sounds, for the men above
were sending down more air than could escape by the valve behind the
helmet, and thus were filling his dress to such an extent that he had a
tendency to rise off the ground despite his weights. To counteract this
he opened the valve in front, let out the superabundant air, got on his
knees, and was soon busy at work inserting the charge-tube into the hole
and tamping it well home, taking care that the fine wire with which it
communicated with the party in the barge should not be injured.

While thus engaged he was watched, apparently with deep interest, by a
small crab, a s