to
breathe while at work, it also entails dangers and difficulties from
which the old method is free. An imperfect supply of air may cause the
bursting of a blood-vessel. Fouling of the lines might not only cut off
the air supply entirely, but prevent the man, anchored by his heavy
dress under twenty fathoms of water more or less, from signalling the
man at the life-line. As on dry land, there are holes and precipices at
the bottom of the sea to be avoided.
In
some seas there are swift currents and as the dress-diver remains under
water for some time, instead of returning at once like his naked
brother, he must keep moving with it, and as he moves, the boat must
move in unison and his tender must keep the lines free. Both diver and
tender must be skilful and alert to do this. Nor is it always easy in
deep-sea diving to find the oysters. They lie in scattered bunches,
often hidden by sponges, coral or other sea growths, their gray or
moss-grown exteriors scarcely to be distinguished from the
surroundings ; if in mud, only an inch or so of the sharp lips of the
two valves projecting above the surface are in evidence; while if in
stooping to 13 193
