at a considerable distance, their protruding air-pipes,
and he had instructed the officers in charge of the
boats to make an especial attack upon these. If the
air-pipes of a crab could be rendered useless, the crew
must inevitably be smothered.

But the brave captain did not know that the
condensed-air chambers of the crabs would supply their
inmates for an hour or more without recourse to the
outer air, and that the air-pipes, furnished with
valves at the top, were always withdrawn under water
during action with an enemy. Nor did he know that
the glass blocks under the armour-plates of the crabs,
which were placed in rubber frames to protect them from
concussion above, were also guarded by steel netting
from injury by small balls.

Valiantly the boats beset the crabs, keeping up a
constant fusillade, and endeavouring to throw grapnels
over them. If one of these should catch under an
overlapping armour-plate it could be connected with the
steam windlass of the Adamant, and a plate might be
ripped off or a crab overturned.

But the crabs proved to be much more lively fish
than their enemies had supposed. Turning, as if on a
pivot, and darting from side to side, they seemed to be
playing with the boats, and not trying to get away from
them. The spring armour of Crab K interfered somewhat
with its movements, and also put it in danger from