AEROSTATION.
In our article on AERONAUTICS Vol. I. we have given a very full account of the history of aerial navigation, and of the method of constructing, filling, and using balloons, as well as the different pieces of apparatus connected with them. Since that article was printed, no essential improvements have been made upon bal loons, although numerous aerial voyages have been performed in this country by the two Mr. Saddlers, Mr. Graham, and Mr. Green; of whom Mr. Saddler, jun. and Mr. Graham have fallen victims to their in trepidity.
Before the general introduction of gas illumination, it was both an expensive and a troublesome operation to fill balloons, even when they were of small size and intended only for amusing experiments. Now, how ever, that in almost every town coal gas is manufac tured, the filling of balloons either for aeronautical ascents, or for the purposes of amusement, has become very easy. The gas obtained from coal is sufficiently light to make a balloon, filled with it, rise with a con siderable ascensive power. The specific gravity of coal gas varies from one-third to two-thirds of that of atmospheric air; but the gas obtained from oil varies from two-thirds to nearly the same specific gravity as atmospheric air, so that it is entirely unfit for aerostatic purpo se S.
One of the simplest and most beautiful experiments in aerostation is to take a turkey's maw or stomach, properly prepared,* and to fill it either with pure hy drogen gas, or the carburctted hydrogen produced from coal. If it is allowed to escape in the open air it will ascend rapidly in the atmosphere; but the best method of showing the experiment is to let it off in a high staircase, and observe it ascend to the cupola, where it will remain near the highest point till the escape of the gas allows it to descend.
Small balloons, either for rising with rarefied air, or with hydrogen gas, may be made by pasting to gether gores of lawn paper cut out as shown in Fig. 5. of Plate III. of AERONAUTICS. If they are intended for rarefied air, their lower ends must be pasted round a slender hoop, from which proceed several wires ter minating in a kind of basket sufficiently strong to sup port a sponge dipped in strong spirits of wine. When the spirits are set on fire their combustion will pro duce a much greater degree of heat than any ordinary flame, and by thus rarefying the air within the balloon will enable it to rise with great rapidity and to a very considerable height.
If the balloon is to be filled with hydrogen gas, the paper should be well varnished; the lower end of the gores should terminate by being pasted round a small tube sufficient for admitting the gas, and capable of being completely closed after the gas is introduced. When the balloon is filled it will then rise with facility in the atmosphere.
The new varnish invented by Charles Mackintosh, Esq. Glasgow, and made by the dissolution of caout chouc, or the naptha obtained from coal tar, is pecu liarly fitted for rendering balloons strong and air tight.