all reasonable that, in this its progress upward, the original velocity should be accelerated. On the other hand, I was not aware that, in any recorded ascension, a diminution had been proved to be apparent in the absolute rate of ascent; although such should have been the case, if on account of nothing else, on account of the escape of gas through balloons ill-constructed, and varnished with no better material than the ordinary varnish. It seemed, therefore, that the effect of such escape was only sufficient to counterbalance the effect of the acceleration attained in the diminishing of the balloon's distance from the gravitating centre. I now considered that, provided in my passage I found the medium I had imagined, and provided that it should prove to be essentially what we denominate atmospheric air, it could make comparatively little difference at what extreme state of rarefaction I should discover it – that is to say, in regard to my power of ascending – for the gas in the balloon would not only be itself subject to rarefaction, (in proportion to the occurrence of which, I could suffer an escape of so much as would be requisite to prevent explosion,) but, being what it was, would, at all events, continue specifically lighter than any compound whatever of mere nitrogen and oxygen. There was a chance – in fact, there was a strong probability – that, at no epoch of my ascent, I should reach a point where the united weights of my immense balloon, the inconceivably rare gas within it, the car, and its contents, should equal the weight of the mass of the surrounding atmosphere displaced; and this will be readily understood as the sole condition upon which my upward flight would be arrested. But if this point were even attained, I could dispense with the ballast and other weight to the amount of nearly 300 pounds. In the meantime, the force of gravitation would be constantly diminishing, in proportion to the squares of the distances, and so, with a velocity prodigiously accelerating, I should at length arrive in those distant regions where the force of the earth's attraction would be superseded by that of the moon.
There was another difficulty, however, which occasioned me some little disquietude. It has been observed, that, in balloon ascensions to any considerable height, besides the pain attending respiration, great uneasiness is experienced about the head and body, often accompanied with bleeding at the nose, and other symptoms of an alarming kind, and growing more and more inconvenient in proportion to the altitude attained2. This was a reflection of a nature somewhat startling. Was it not probable that these symptoms would increase until terminatated by death itself? I finally thought not. Their origin was to be looked for in the progressive removal of the customary atmospheric pressure upon the surface of the body, and consequent distention of the superficial blood-vessels – not in any positive disorganization of the animal system, as in the case of difficulty in breathing, where the atmospheric density is chemically insufficient for the due renovation of blood in a ventricle of the heart. Unless for default of this renovation, I could see no reason, therefore, why life could not be sustained even in a vacuum; for the expansion and compression of chest, commonly called breathing, is action purely muscular, and the cause, not the effect, of respiration. In a word, I conceived that, as the body should become habituated to the want of atmospheric pressure, the sensations of pain would gradually diminish – and to endure them while they continued, I relied with confidence upon the iron hardihood of my constitution.
2 Since the original publication of Hans Pfaall, I find that Mr Green, of Nassau-balloon notoriety, and other late æronauts, deny the assertions of Humboldt, in this respect, and speak of a decreasing inconvenience, – precisely in accordance with the theory here urged.
Thus, may it please your Excellencies, I have detailed some, though by no means all, the considerations which led me to form the project of