Something’s in the air.
Should the reader entertain the theory that books showily printed on calendered paper, with abundant illustrations, more or less splurgy, are not particularly apt to prove attractive reading, we cannot say that Travels in Space will tend to convince him he has been wrong; albeit the nature of its subject renders it readable. It would be unreasonable to expect it to present the strange experiences of ballooning with all that life and reality that Mr. Bacon’s By Land and Sky did, last year, because that was a masterpiece. A glance at the volume will inform him that it is not a work of research, like Mr. Chanute’s Progress in Flying-Machines, from which, by the way, it copies extensively, almost verbatim, without acknowledgment, and to which it is vastly inferior in all respects in which the two works come into comparison, excepting in a very few details. It is later in date by more than eight years, and its scope is wider. The field still remains open, however, for a really workmanlike history of aeronautics.
The building of an airship is as much more difficult than the building of a steamer, like the Kaiser Willtetni II, as the latter is than the throwing of a trussed suspension-bridge across the North River. Consequently, Mr. Walker has judged a duodecimo of a hundred and fifty pages to be the proper sort of volume in which to convey the airship-building art. For, once problems reach a certain pitch of difficulty, and the more profound they are, the less is the knowledge generally thought requisite for attacking them. The first chapter of Mr. Walker’s “practical” book is entitled The Laws of Flight. The only statement of a law which it contains as the following:
When a moving body is directly opposed by a vis mortua, such as a pressure or resistance like that of gravity, the measure of such vis mortua required to neutralize the force [of the moving body] and bring the moving body to rest must form the basis of the measurement of the force.
Thus, the persons who Mr. Walker assumes are to undertake the construction of airships, and for whose encouragement, he has provided his handbook, are supposed to be in need of this information, while further dynamical science, he would appear to presume, is quite beyond their comprehension. Later in the book, it appears that they are persons who need to be told what a sine and cosine are. What Mr. Walker fails to tall them, but, on the contrary, implicitly denies, is that, with such an outfit, they will make great fools of themselves if they undertake the building of an airship.
Vessels to sail the air are of four types. The first is that of a machine with ascensional power, but with no motor. Such is a simple balloon or other aerostat, a kiteballoon, or a system of attached balloons. Much may be done with s skilfully managed balloon. Its great advantage over other air-sailing vessels lies In its comparative safety. Let any other kind of airship decisively come to grief, and instant death ensues for all its crew. But if a balloon bursts, not too near the ground, the calm and skilful aeronaut can take measures to save himself. This accident happened to Wise in Pennsylvania, in 1836, at an elevation of 13,000 feet, but he was so far from being reduced to a pulp by the fall that, jumping up, he remarked upon the heat of the lower atmosphere, and, before many minutes had elapsed, had determined to repeat the experiment at the first opportunity. The fatal fails (other than drowning cases) have usually been from moderate heights, or have been due to the fright or inexperience of the operator. When Simmons met his death in 1888, he fell only 50 feet; yet neither of his two companions was killed, and one of them was not even injured. Capt. Dale’s balloon in 1892 burst at a height of 600 feet, he and Mr. Shadbolt, a professional aeronaut, being killed, while two amateurs who were with them escaped unhurt, but experts opined that with proper management all might have been saved. This comparative immunity arises from the fact that the lower half of a failing balloon of the ordinary shape invariably cups into the upper half, forming the best of parachutes. Immunity, therefore, does not extend to aerostats stiffened with hoops or made of aluminium. A serious fault of the ordinary balloon is that there is no level at which it is in equilibrium unless the gas be confined, which is too unsafe. When it goes up, it retains the same ascensional force, and continues to be accelerated upward until it loses gas; and its momentum of perhaps a couple of tons moving four or five hundred feet per second will carry it up long after the gas has so swelled and spilled that, by the time it ceases to rise, it is much heavier than the air, and would come down to earth if ballast were not thrown out, and so it goes, alternately rising and falling until its ascensional power is quite wasted. Mr. Walker does not make this matter at all clear, but talks, as aeronauts are apt to do, of the level “to which the balloon must rise,” just as if it wore a closed bottle. A metallic balloon would be free from this objection, having a definite level at which, if tight, it would remain in equilibrium, or oscillate above and below it, indefinitely Schwarts’s machine of 1894 demonstrated that an aluminium balloon can be made sufficiently light (its ascensional power must have been about 7,000 lbs.) and can be filled with hydrogen; but it is very unfortunate that the inexperienced operator took fright and destroyed the airship, though not his miserable self, before it load risen high enough to show whether or not at its level of equilibrium it would have been able to withstand the pressure of gas within. The excess of gas would naturally be allowed to escape, but if this escape were too rapid, all the advantage of the metallic construction would be lost, while if it were not very rapid, the excess of pressure from within would become very considerable. Though such things are subject to calculation, actual experience is extremely welcome. To-day it is probable that such a vessel would be made of magnalium, not of pure aluminium. Somebody with a spare million could make an interesting experiment by combining the metallic balloon with a suggestion of the celebrated Monge that has never yet been tried. He was eminently a practical man as well as a mathematician of the first order. His suggestion was that of an airsnake, to be composed of twenty-five aerostats strung together, the vermicular or serpentine motion being brought about in a vertical plane by the transfer of ballast from one to another.