We got upstairs through the aperture, and found ourselves on the flat roof of the building, but precisely underneath the air-ship; we entered, however, the open trap constructed in the latter, for we soon found out that the weather was bitterly cold. This, unfortunately, prevented me from becoming more intimately acquainted with the outward appearance of the balloon, and with its locomotive powers. On the other hand, ample opportunity was afforded us for examining its internal arrangements. As soon as we came into what I can but term the "hold" of the vessel, Bacon called my attention to a long narrow cylinder which ran across the whole length of the ship. "Therein lies," said he, "the whole secret of aëronautics. In order that I may explain this to you, I must remind you of this, that it was formerly impossible to steer any balloon except before the wind. An ordinary vessel, when the keel cuts through the water, can sail half or quarter-wind, because she moves in the two intermediate matters of air and water, the latter offering a greater resistance than the former, and thereby supporting the vessel in her movements; to which must be added that the resistance operates in a definite direction, namely, in that of the motion of the ship, so that by supplying the craft with a rudder or helm one is able to turn her at pleasure to the right or the left. "But," continued Bacon, "this becomes quite a different matter when a vessel is merely surrounded by air. Driven onward by the wind, which means carried along by the atmospheric current, she meets with no resistance, and therefore lacks every point of support whereby to turn herself. She will always offer the largest of her sides to the wind, which falls upon it at right angles, just the same as on a light piece of paper or cloth whirled round by the wind.