Page:Popular Science Monthly Volume 89.djvu/39

 Popular Science Moiillih/

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��rcquirt'iiK'nts are a riKxlcratfly large, level space, a gas-main several inrhes in diameter, a cartload of sand, two dozen sandbags (eight by sixteen inches, with four one-foot cords collected in a hook around their open end), and plenty of strong men who aren't afraiil to hold on to the bag.

The outer part of the empty rolled gas-bag is the short hose, called appendix, at the balloon's lower end. A short cylinder of equal diameter is slipped into its end, and a longer hose of balloon cloth is stripped over both and securely tied around them. The other end of the hose is similarly tied to the outlet of the gas-main, whereujjon the bag is unrolled and spread around the appendix as the center. The seam of the round opening on top of the bag is tightly screwed into the circumference of the valve. The seam of the similar opening in the net is buckled to the same margin by a circle of short straps. The net is spread in the same manner, and a wide circle of sandbags, previously filled, is built around the spread bag and net and hooked into the meshes.

How the Balloon is Inflated Once the gas is turned on it dilates the hose with a roaring sound, rush- ing into the balloon and raising the center of the spread. You have the impression that the gas which finds it so hard to puff out the cloth could never lift a man, but you do not realize the physical fact that the buoyancy is increasing continually with the addition- al space occupied by gas. Soon the meshes of the net begin to pull the bag hooks, and since the circle occupied by the spread

��Q

��cloth narrows

�with the

�in-

�creasing infla-

�tion the

�bags

�must

�b c

�moved

�1 n

�gradually

�and

�evenly.

� �It is

�a n

�interest

�ing

�sight to see the

�balloon g

�row

�like a moun-

��FIG 8

��lain out of a circle of cloth. E\'en after

the buoyancy increases the sandbags

lash it firmly, for their total weight is far

greater than the maximum lift, and their

indixidual weight oxercomes (he fraction

of lilt e.xerted by the mesh to which each

is hooked. As the f)ags narrow in on the

net they crowd together. Finally they

reach the lowest meshes and are lifted

from the ground by the attendants.

Then the fully inflated balloon,

now permitted to rise sufficiently

to untie the hose from the appendix,

is led to the basket nearby.

The ends of the ropes into which j^ the net issues are hooked by loops

to the "collecting ring" above the basket, and the hooks are now released from the meshes and put over the ropes. By sliding them slowly in toward the basket the balloon is allowed to rise to its normal position above the basket by finally hooking clusters of bags around the lower ends of the stout basket-ropes. After a few details have been attended to, such as tying the appendix with a knot, which can be jerked open while ascend- ing, and arranging valve, rip-cords; ballast-bags and instruments, the passen- gers climb in.

The Start of an Ascension The wind soon pulls the basket "off its feet" and there is considerable bumping and scraping, during which it is a convenient thing for those inside to have an "upper berth." Following this comes the ticklish process of tentatively taking off sandbags until the lift is supposedly equal to the load and of li'tting the raised basket go for a moment to see whether it will fall or rise. When the final "let go" is given

the excitement begins.

During the first moments of rising there is that f|ueer sensation of riding in an endless eleva- tor or Ferris- wheel. Soon this is forgot- ten in a world of silence.

���An air-tight attachment must be made between the gas hose and the appendix

�� �