306 SCIENTIFIC RECREATIONS. 



A very small quantity of ballast thrown away will make a great differ- 

 ence; a handful will raise the balloon many feet, and a chicken bone cast out 

 occasions a rise of thirty yards. The ballast is carried in small bags, and 

 consists of dry sand, which speedily dissipates in the air as it falls. By 

 throwing out ballast the aeronaut can ascend to a great height in fact, as 

 high as he can go, the limit apparently for human existence being about 

 seven miles, when cold and rarefied air will speedily put an end to existence. 

 It is a curious fact, that however rapidly the balloon may be travelling 

 through the air, the occupants are not sensible of the motion. This, in part, 

 arises from the impossibility of comparing it with other objects. We pass 

 nothing stationary which would indicate the pace at which we travel. But 

 the absence of oscillation is also remarkable ; even a glass of water may be 

 filled brim-full, and to such a level that the water is above the rim of the 

 glass, and yet not a drop will fall. This experiment was made by M. 

 Flammarion. When the aeronaut has ascended some distance the earth 

 loses its flat appearance, and appears as concave as the firmament above. 

 Guide ropes are usually attached to balloons, and as they rest upon the 

 ground they relieve the balloon of the amount of weight the length trailing 

 would cause. They thus act as a kind of substitute for ballast as the 

 balloon is descending. Most of the danger of aerial travelling lies in the 

 descent ; and though in fine weather the aeronaut can calculate to a nicety 

 where he will descend on a windy day, he must cast a grapnel, which catches 

 with an ugly jerk, and the balloon bounds and strains at her moorings. 



Although many attempts have been made to guide balloons through 



the air, no successful apparatus has ever been completed for use. Paddles, 



sails, fans, and screws have all been tried, but have failed to achieve the 



desired end. Whether man will ever be able to fly we cannot of course say. 



In the present advancing state of science it may not be impossible ere long 



to supply human beings with an apparatus worked by electricity, perhaps, 



which will enable them to mount into the air and sustain themselves. But 



even the bird cannot always fly without previous momentum. A rook will 



Tun before it rises, and many other birds have to " get up steam," as it were, 



before they can soar in the atmosphere. Eagles and such heavy birds find 



it very difficult to rise from the ground. We know that vultures when 



gorged cannot move at all, or certainly cannot fly away ; and eagles take 



up their positions on high rocks, so that they may launch down on their 



prey, and avoid the difficulty of rising from the ground. They swoop down 



with tremendous momentum and carry off their booty, but often lose their 



lives from the initial difficulty of soaring immediately. We fear man's 



weight will militate against his ever becoming a flying animal. When we 



obtain a knowledge of the atmospheric currents we shall no doubt be able 



to navigate our balloons ; but until then and the information is as yet 



very limited, and the currents themselves very variable we must be content 



to rise and fall in the air, and travel at the will of the wind in the upper 



regions of the atmosphere. 



