rly for this invitation and I follow Captain
Hodgson from the control-platform, stooping low to avoid the bulge
of the tanks. We know that Fleury's gas can lift anything, as the
world-famous trials of '89 showed, but its almost indefinite powers
of expansion necessitate vast tank room. Even in this thin air the
lift-shunts are busy taking out one-third of its normal lift, and still
"162" must be checked by an occasional downdraw of the rudder or our
flight would become a climb to the stars. Captain Purnall prefers an
overlifted to an underlifted ship; but no two captains trim ship alike.
"When I take the bridge," says Captain Hodgson, "you'll see me shunt
forty per cent of the lift out of the gas and run her on the upper
rudder. With a swoop upward instead of a swoop downward, as you say.
Either way will do. It's only habit. Watch our dip-dial! Tim fetches her
down once every thirty knots as regularly as breathing."

So is it shown on the dip-dial. For five or six minutes the arrow creeps
from 6700 to 7300. There is the faint "szgee" of the rudder, and back
slides the arrow to 6000 on a falling slant of ten or fifteen knots.

"In heavy weather you jockey her with the screws as well," says Captain
Hodgson, and, unclipping the jointed bar which divides the engine-room
from the bare deck, he leads me on to the floor. Here we find Fleury's
Paradox of the Bulk-headed Vacuum--which we accept now without
thought--literally in full blast. The three engines are H.T.&T.
assisted-vacuo Fleury turbines running from 3000 to the Limit--that is
to say, up to the point when the blades make the air "bell"--cut out a
vacuum for themselves precisely as over-driven marine propellers used
to do. "162's" Limit is low on account of the small size of her nine
screws, which, though handier than the old colloid Thelussons, "bell"
sooner. The midships engine, generally used as a reinforce, is not
running; so the port and starboard turbine vacuum-chambers draw direct
into the return-mains.

The turbines whistle reflectively. From the low-arched expansion-tanks
on either side the valves descend pillarwise to the turbine-chests,
and thence the obedient gas whirls through the spirals of blades with a
force that would whip the teeth out of a power saw. Behind, is its own
pressure held in leash of spurred on by the lift-shunts; before it,
the vacuum where Fleury's Ray dances in violet-green bands and whirled
turbillons of flame. The jointed U-tubes o