It used commonly to be asserted, and is so often to this day, that a feeling as of sea-sickness is experienced in balloon travel, and the notion has undoubtedly arisen from the circumstances attending an ascent in a captive balloon. It were well, now that ballooning bids fair to become popular, to disabuse the public mind of such a wholly false idea. The truth is that a balloon let up with a lengthy rope and held captive will, with a fitful breeze, pitch and sway in a manner which may induce all the unpleasant feelings attending a rough passage at sea. It may do worse, and even be borne to earth with a puff of wind which may come unexpectedly, and considerably unsettle the nerves of any holiday passenger. I could tell of a "captive" that had been behaving itself creditably on a not very settled day suddenly swooping over a roadway and down into public gardens, where it lay incontinently along the ground, and then, before the astonished passengers could attempt to alight, it was seized with another mood, and, mounting once again majestically skyward, submitted to be hauled down with all becoming grace and ease. It is owing to their vagaries and want of manageability that, as will be shown, "captives" are of uncertain use in war. On the other hand, a free balloon is exempt from such disadvantages, and at moderate heights not the smallest feeling of nausea is ever experienced. The only unpleasant sensation, and that not of any gravity, ever complained of, is a peculiar tension in the ears experienced in a rapid ascent, or more often, perhaps, in a descent. The cause, which is trivial and easily removed, should be properly understood, and cannot be given in clearer language than that used by Professor Tyndall:--"Behind the tympanic membrane exists a cavity--the drum of the ear--in part crossed by a series of bones, and in part occupied by air. This cavity communicates with the mouth by means of a duct called the Eustachian tube. This tube is generally closed, the air space behind the tympanic membrane being thus cut off from the external air. If, under these circumstances, the external air becomes denser, it will press the tympanic membrane inwards; if, on the other hand, the air on the other side becomes rarer, while the Eustachian tube becomes closed, the membrane will be pressed outwards. Pain is felt in both cases, and partial deafness is experienced.... By the act of swallowing the Eustachian tube is opened, and thus equilibrium is established between the external and internal pressure."