Airships past and present, together with chapters on the use of balloons in connection with meteorology, photography and the carrier pigeon . he usualway. He proposed to exhaustthe air from the metal spheresby filling them with waterthrough an opening at the top,and then allowing the waterto flow away through a tap atthe bottom. He assumed thata vacuum would be created ifthe tap at the bottom wereclosed at the right order to prevent the boatfrom starting with a suddenjerk it was to be suitablyloaded with weights ; the height to which it would rise wouldthen be conveniently regulated
Airships past and present, together with chapters on the use of balloons in connection with meteorology, photography and the carrier pigeon . he usualway. He proposed to exhaustthe air from the metal spheresby filling them with waterthrough an opening at the top,and then allowing the waterto flow away through a tap atthe bottom. He assumed thata vacuum would be created ifthe tap at the bottom wereclosed at the right order to prevent the boatfrom starting with a suddenjerk it was to be suitablyloaded with weights ; the height to which it would rise wouldthen be conveniently regulated either by the admission of air tothe spheres, or by throwing overboard some portion of the ideas on the theory of the problem were undoubtedly correct,and he carried on a vigorous controversy with those who advancedobjections to his proposals. But he came finally to the piousconclusion that he could scarcely hope for the accomplishmentof his scheme, seeing that God would prevent such a revolutionin human affairs. In the year 1680 Borelli makes some interestingobservations with regard to the construction of an artificial b 2. Fig. 2.—Fauste Veranzio in his parachute. AIRSHIPS PAST AND PRESENT. bird in his book De Motu Animalium, and tried to show thatit was impossible for a man to fly by his own unaided man was, indeed, much too heavy, at any rate in comparisonwith birds, neither had he sufficient muscular energy in the partsabout the chest; and further, the weight of any appurtenancesto take the place of wings would place him at a still moreserious disadvantage. This reminds us of the results publishedby Helmholtz in 1872, when he was a member of the committee appointed to examine intoaeronautical problems. Hethere states in the most definitemanner that it is extremelyimprobable that, with the aidof the most perfect mechanism,a man will be able by his ownmuscular exertion to raise hisbody into the air and to main-tain it in that position. But Borelli gav
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