Suppose that my motor and propeller push me through the air at the rate of 20 miles an hour, I am in the position of a steamboat captain whose propeller is driving him up or down the river at the rate of 20 miles an hour. Imagine the current to be 10 miles per hour. If he navigates against the current he accomplishes 10 miles an hour with respect to the shore, though he has been travelling at the rate of 20 miles an hour through the water. If he goes with the current he accomplishes 30 miles an hour with respect to the shore, though he has not been going any faster through the water. This is one of the reasons why it is so difficult to estimate the speed of an air-ship.
It is also the reason why air-ship captains will always prefer to navigate for their own pleasure in calm weather, and, when they find an air current against them, will steer obliquely upward or downward to get out of it. Birds do the same thing. The sailing yachtsman whistles for a fair breeze, without which he can do nothing, but the river steamboat captain will always hug the shore to avoid the freshet, and will time his descent of the river by the outgoing, rather than the incoming, tide. We air-shipmen are steamboat captains and not sailing yachtsmen.
The navigator of the air, however, has the one great advantage—he can leave one current for another. The air is full of varying currents. Mounting, he will find an advantageous breeze or else a calm. These are strictly practical considerations, having nothing to do with the air-ship's ability to battle with the breeze when obliged to do it.
Before going on my first trip I had wondered if I should be sea-sick. I foresaw that the sensation of mounting and descending obliquely with my shifting weights might be unpleasant. And I looked forward to a good deal of pitching (tangage), as they say on board ship—of rolling there would not be so much—but both sensations would be novel in ballooning, for the spherical balloon gives no sensation of movement at all.
In my first air-ship, however, the suspension was very long, approximating that of a spherical balloon. For this reason there was very little pitching. And, speaking generally, since that time, though I have been told that on this or that trip my air-ship pitched considerably, I have never been sea-sick. It may be due in part to the fact that I am rarely subject to this ill upon the water. Back and forth between Brazil and France and between France and the United States I have had experience of all kinds of weather. Once, on the way to Brazil, the storm was so violent that the grand piano went loose and broke a lady's leg, yet I was not sea-sick.
I know that what one feels most distressingly at sea is not so much the movement as that momentary hesitation just before the boat pitches, followed by the malicious dipping or mounting, which never comes quite the same, and the shock at top and bottom. All this is powerfully aided by the smells of the paint, varnish, tar, mingled with the odours of the kitchen, the heat of the boilers, and the stench of the smoke and the hold.
In the air-ship there is no smell—all is pure and clean—and the pitching itself has none of the shocks and hesitations of the boat at sea. The movement is suave and flowing, which is doubtless owing to the lesser resistance of the air waves. The pitches are less frequent and rapid than those at sea; the dip is not brusquely arrested, so that the mind can anticipate the curve to its end; and there is no shock to give that queer, "empty" sensation to the solar plexus.
Furthermore, the shocks of a transatlantic liner are due first to the fore, and then to the after, part of the giant construction rising out of the water to plunge into it again. The air-ship never leaves its medium—the air—in which it only swings.
This consideration brings me to the most remarkable of all the sensations of aerial navigation. On my first trip it actually shocked me! This is the utterly new sensation of movement in an extra dimension!
Man has never known anything like free vertical existence. Held to the plane of the earth, his movement "down" has scarcely been more than to return to it after a short excursion "up," our minds remaining always on the plane surface even while our bodies may be mounting; and this is so much the case that the spherical balloonist as he rises has no sense of movement, but gains the impression that the earth is descending below him.