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loss of 50 degrees Fahrenheit, or about one-tenth of the entire lifting force in a few hours: Ballast to be thrown overboard, 2,000 pounds. In the case of the Zeppelin, twice the volume of the America, all these

[[image]]
[[caption]] FIGHTING TO SAVE THE STRUCTURE FROM COMPLETE DESTRUCTION—THIS STRUGGLE CONTINUED DAY AND NIGHT FOR FOUR WEEKS. 

losses would be doubled. With either ship, it is obvious it would be impossible, under such conditions, to prolong the voyage more than two days and nights, because the exhaustion of buoyant force by these temperature changes would be require the carrying of so much ballast as to leave little room for the carrying of fuel, and it is the fuel-supply, of course, which gives the radius of action.
If the America were to be set out upon a voyage from our base in Spitzbergen, with an air temperature 32 degrees, during the next 24 hours the greatest rise or fall of temperature would be 10 degrees Fahrenheit, involving a loss of 400 pounds of lifting force. If the lightening of the cargo by fuel consumption of the motor were not sufficient to compensate this loss, as much of the weight of

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