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 449 or by hunting for it vertically—it would immediately stop its motor, in order to waste no fuel. Indeed, its propeller-force ought to be exerted only in two cases, for two great uses : (a) to push on straight to the Pole in every period of calm, and (b) to modify the air-ship's course when riding on a more or less favourable air-current.

Such are the two vital advantages of the aerial yacht not enjoyed by André in his balloon—its ability to re-direct its course due north, and time to wait for opportunities to so re-direct its course again and again and again. I will not dwell on the vital comforts of a heated cabin : but to me it is obvious that the closed room of the Polar yacht ought to be constructed very close, to hold all the heat its captain could give it. Its walls of many thicknesses of varnished silk enclosing both motor and boiler might save the expedition ; for, apart from the adventure of André, this would be the first time for men to affront the cold of the north without the resources of continual violent exercise. Indeed, I have often asked myself if André and his companion did not simply perish from cold !

Or another supposition—did it never occur to you that the tragedy of the André expedition might have been due to his balloon descending to earth in those far northern regions? Who knows what practical effect of condensation the intense cold might have had on its gas? A single descent to earth might have occasioned the loss of a great deal of gas. To rise again might have cost André a dangerous loss of ballast: and he would have started off again crippled in both these vital means !

Should the aerial Polar yacht be obliged to descend to earth, its captain could accomplish the manœuvre by merely turning a faucet and allowing the intense cold to condense his gas. To rise again, he would simply re-heat his gas.

When the secret history of the Russo-Japanese war comes to be known, the submarine-boat will probably be found to have played a decisive part in the destruction of the first Russian Navy.

It is astonishing how quickly we habituate ourselves to revolutionary inventions. Up to the moment they burst on us as successes, we condemn them; then we accept them nonchalantly, as something natural.

A few years ago the submarine-boat occupied the same category as the air-ship in our consciousness ; and it is only yesterday that a British submarine-boat drowned its entire crew while under cautious experiment in protected waters! Yet there are few who