180 SCIENCE IN SHOUT CHAPTERS. 



All this blind drifting for hours, during which the bal- 

 loon may be' carried out to sea, and opportunities of safe 

 descent may be lost, is averted in an Arctic balloon voyage, 

 which would be made in the summer, when the sun never 

 sets. There need be no break in the survey of the ground 

 passed over, no difficulty in pricking upon a chart the course 

 taken and the present position at any moment. With an 

 horizon of 50 to 100 miles' radius the approach of such a 

 danger as drifting to the open ocean would be perceived 

 in ample time for descent, and as a glance at the map will 

 show, this danger cannot occur until reaching the latitudes 

 of inhabited regions. 



The Arctic aeronauts will have another great advantage 

 over those who ascend from 'any part of England. They 

 can freely avail themselves of Mr. Green's simple but most 

 important practical invention the drag-rope. This is a 

 long and rather heavy rope trailing on the ground. It per- 

 forms two important functions. First, it checks the pro- 

 gress of the balloon, causing it to move less rapidly than 

 the air in which it is immersed. The aeronaut thus gets a 

 slight breeze equivalent to the difference between the velo- 

 city of the wind and that of the balloon's progress. He 

 may use this as a fulcrum to effect a modicum of steerage. 



The second and still more important use of the drag-rope 

 is the very great economy of ballast it achieves. Suppose 

 the rope to be 1000 feet long, its weight equal to 1 Ib. for 

 every ten feet, and the balloon to have an ascending power 

 of 50 Ibs. It is evident that under these conditions the 

 balloon will retain a constant elevation of 500 feet above 

 the ground below it, and that 500 feet of rope will trail 

 upon the ground. Thus, if a mountain is reached no bal- 

 last need be thrown away in order to clear the summit, as 

 the balloon will always lift its 500 feet of rope, and thus 

 always rise with the up-slope and descend with the down- 

 slope of hill and dale. The full use of this simple and 

 valuable adjunct to aerial traveling is prevented in such a 

 country as ours by the damage it might do below, and the 

 temptation it affords to mischievous idiots near whom it 

 may pass. 



In the course of many conversations with various people 



