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huge ship by a storm of wind while she was moored to the ground, that led to the disaster.

If the Zeppelin had been navigating the air over the polar ocean, in July or August, she would have escaped this calamity. The maximum change of temperature likely to be encountered there in any 24 hours is 10 degrees Fahrenheit; and the usual diurnal variation is only half as much. This evenness of temperature is due, of course, to the absence of the alternating day and night; it is all day there at that season, the sun high in the heavens even at midnight.

Again, what is known as the guide-rope method, but for which equilebrator is a better word, cannot be used save on rare occasions, in settled countries, and may be used whenever necessary in the Arctic regions, where there are no forests, buildings, electric wires or other obstructions in the way. The Zeppelin had no equilebrator; the America is fitted with one weighing 1,200 pounds, ready for use whenever necessary to deposit a part of that weight upon the surface of the earth, to keep the ship from descending and to avoid the throwing overboard of ballast to accomplish the same purpose. A guide-rope or equilebrator is simply ballast which may be used without losing it. Our equilebrator is the much-talked of “stuffed serpent” or “sausage,” a long steel-scaled cylinder of leather, water-tight, buoyant in water, and 75 per cent of its whole weight made up of reserve food for the crew.

Thus we see in summary that in the polar regions we escape the greater part of the evil which afflicts aerostats in the temperate zones—loss of vitality through alternating expansions and contractions of the gas—–and in the north we are able to employ a simple device for minimizing what difficulty there is from this source. The difference is a very great one, and may be made clear by a simple statement of three assumed voyages—–the America and the Zeppelin in the temperate zones, and the America in the Arctic regions. 

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