The _Preussen_ was one of the largest passive balloons ever constructed. In cubic capacity it was comparable with the colossal _Montgolfière_, _La Flesselle_, already described, and the huge free balloon _Le Geant_, constructed by Nadar in 1863. But all were eclipsed by the great balloon of Henri Giffard. This latter measured 450,000 cubic feet, and even to-day ranks as the largest captive balloon ever constructed. It was a familiar object at the Paris Exposition of 1878, where it was installed by the famous inventor Henri Giffard, to give sightseers a bird’s-eye view of Paris. It could take up forty persons at one time, or eight more than once ascended in Nadar’s _Geant_. No serious attempt has been made to surpass the altitude flight of Professor Berson and Dr. Süring; for though it is easily possible to carry human beings to a greater height than seven miles, the results seem hardly to justify the cost. To ascend very much higher would require an enormous and costly balloon, and to ensure the comfort of the passenger might require an air-tight car, or armor supplied continuously with fresh air, or oxygen. Such a suit, or car, however, can be made very light, since its pressure must naturally be internal; and it would admit of an extremely rapid change of elevation without discomfort to the passenger. A steel bottle weighing fifty pounds, and filled with compressed air, or oxygen, would supply a passenger several hours, and allow him to breathe under normal pressure. The total weight of a bottle and air-tight car, or suit, need not exceed the weight of a man. Moreover, the ballast could be largely dispensed with, thus admitting of a very rapid ascent from the earth. A celluloid car would have the advantage of transparency, though it might become too brittle at very low temperatures. A suit, or car, with glass portholes would serve in lieu of a celluloid car for transparency. The usual balloon and basket, carrying a steel bottle, furnishing air at normal pressure to a man in a rubberized silk suit is a sufficiently simple and practicable device; the air entering the suit near his mouth and leaving below through a check valve regulated to maintain the desired internal pressure. An air-tight silk fabric capable of enduring safely a tensile stress of 150 pounds per running inch would answer the purposes. But at present there seems to be no incentive to attempt a balloon trip exceeding the heights already attained, unless it be that of notoriety or sentiment.