With a swoop upwards instead of a swoop downwards, 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 6,700 to 7,300. There is the faint "szgee" of the rudder, and back slides the arrow to 6,500 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 Bulkheaded Vacuum—which we accept now without thought—literally in full blast. The three engines are H. T. &. T. assisted-vacuo Fleury turbines running from 3,000 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 or spurred on by the lift-shunts; before it, the vacuum where Fleury's Ray dances in violet-green bands and whirled turbillions of flame. The jointed U-tubes of the vacuum-chamber are pressure-tempered colloid (no glass would endure the strain for an instant) and a junior engineer with tinted spectacles watches the Ray intently. It is the very heart of the machine—a mystery to this day. Even Fleury who begat it and, unlike Magniac, died a multi-millionaire, could not explain how the restless little imp shuddering in the U-tube can, in the fractional fraction of a second, strike the furious blast of gas into a chill grayish-green liquid that drains (you can hear it trickle) from the far end of the vacuum through the eduction-pipes and the mains back to the bilges. Here it returns to its gaseous, one had almost written sagacious, state and climbs to work afresh. Bilge-tank, upper tank, dorsal-tank, expansion-chamber, vacuum, main-return (as a liquid), and bilge-tank once more is the ordained cycle. Fleury's Ray sees to that; and the engineer with the tinted spectacles sees to Fleury's Ray. If a speck of oil, if even the natural grease of the human finger touch the hooded terminals Fleury's Ray will wink and disappear and must be laboriously built up again. This means half a day's work for all hands and an expense of one hundred and seventy-odd pounds to the G. P. O. for radium-salts and such trifles.

"Now look at our thrust-collars. You won't find much German compo there. Full-jewelled, you see," says Captain Hodgson as the engineer shunts open the top of a cap. Our shaft-bearings are C. M. C. (Commercial Minerals Company) stones, ground with as much care as the lens of a telescope. They cost £37 apiece. So far we have not arrived at their term of life. These bearings came from "No. 97," which took them over from the old "Dominion of Light," which had them out of the wreck of the "Perseus" aëroplane in the years when men still flew linen kites over thorium engines!

They are a shining reproof to all low-grade German "ruby" enamels, so-called "boort" facings, and the dangerous and unsatisfactory alumina compounds which please dividend-hunting owners and turn skippers crazy.

The rudder-gear and the gas lift-shunt, seated side by side under the engine-room dials, are the only machines in visible motion. The former sighs from time to time as the oil plunger rises and falls half an inch.