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The National Geographic Magazine 



come in contact with the ice without in- 

 jury — there must come an angle, no mat- 

 ter how great the power of the wind, 

 when the downward thrust of its press- 

 ure would be offset by the ascending 

 power of the balloon, thus relieved of a 

 considerable part of its weight. But even 

 then there would be the hazard of dis- 

 aster due to pounding, to plunging up 

 and down with the fluctuating force of 

 the wind, and to the other causes already 

 spoken of. 



For reasons which have been already 

 pointed out, it was, in my opinion, im- 



miles per hour. That will mean about 

 250 kilogrammes of resistance, and it 

 should be secured with a cable weighing 

 about 300 kilos, perhaps less. The sur- 

 face of the ice offers almost ideal facili- 

 ties for the operation of such a device, 

 and it is perhaps the only place in the 

 world where this method could be suc- 

 cessfully employed over a wide area. 



If we arrange our retardateur for 

 working up to, say, 12 miles per hour, with 

 ample margin of strength in all parts, we 

 shall know that this is approximately the 

 maximum stress that can ever be put 



<V)vvC«. "i. 



perative that the plan of retaining contact 

 with the surface of the earth through the 

 guide-rope equilebreur, and occasionally 

 by anchorage, should be adhered to. 



We shall not attempt to make firm 

 anchorage, save in calms or very light 

 airs, and then only for special purposes, 

 such as scientific observations. In lieu 

 thereof we shall employ the principle of 

 the dragging anchor. When adverse 

 winds of relatively high velocity are en- 

 countered, instead of throwing out a 

 grappling hook we shall let trail over the 

 ice a steel cable provided with small pro- 

 jections, like hooks or rings, calculated 

 to give a resistance equal to the pull of 

 the airship in a wind of about 12 to 15 



upon it. There will be no danger of the 

 work being quadrupled by an increase of 

 the velocity of the wind up to 30 or 40 

 miles per hour. 



With a wind of 10 to 12 miles per hour 

 we shall remain approximately stationary 

 in the air, perhaps drifting half a mile or 

 a mile per hour. In a wind of 15 miles 

 per hour we should drift about 3 miles 

 per hour with it. In a wind of 20 miles 

 per hour the driftage should be 8 miles 

 per hour. Should the wind rise to 30 

 miles per hour the driftage should be 

 about 18 miles per hour. Thus in the 

 higher winds we should lose way accord- 

 ing to the velocity, but in no case would 

 we incur risks of rupture of our appa- 



