If the reader is desirous of calculating either for model balloons, or, as to the size, capacity, and power of larger balloons, take note of this concise and abridged table of the diameters, surfaces, and capacities, together with the ascensive power for every foot capacity for hydrogen, so that if coal gas is used, allowance must be made accordingly.
First, for miniature paper or skin balloons.
| Feet, Diameter. | Surface in Square. | Capacities in Cubic Feet. | Pounds Ascensive Power. | |||
| 1 | 3 | 1⁄10 | 0 | 1⁄2 | 0 | 2⁄32 |
| 3 | 28 | 14 | 1 | in nearly a pound. | ||
| 6 | 113 | 113 | 7 | |||
| 10 | 314 | 523 | 33 | |||
| 20 | 1,257 | 4,189 | 261 | |||
| LARGER BALLOONS. | ||||||
| 30 | 2,827 | 14,137 | 884 | |||
| 40 | 5,026 | 33,510 | 2,094 | |||
| 50 | 7,854 | 65,450 | 4,091 | |||
| 80 | 20,106 | 268,083 | 16,755 | |||
| 100 | 31,416 | 523,599 | 32,725 | |||
The striking advantage of enlarging balloons, arises from the fact, that their powers increase faster than their surfaces. When the diameter is doubled, four times as much material is required, but you get eight times as much capacity.
I have now offered a few plain calculations in order to assist those who feel interested in the subject, they may be extended and more scientifically pursued in another volume of my experiences, when they will be required, perhaps, for illustration of other ascents.
I am often asked, how high will a balloon go? Will it mount higher and higher until gas is let off to stop it?
My answer is, that when a balloon, after inflation, is brought to an even balance, in other words, when so much ballast is placed in the car, that it shows a very slight tendency to move upwards, then the required ascending power is increased by putting out more sand, say to the amount of twenty, thirty, or forty pounds, according to circumstances, I mean the strength of wind at the time, and the proximity of adjacent objects, such as trees and buildings.
With either of these limited number of weights removed, the balloon cannot rise very high, unless there is either a large space for expansion, or a very much larger quantity of sand is put out subsequently.
I will simply try this position by asking the reader to suppose that A and B, two rival aëronauts, are about to engage at one and the same time with two balloons of similar capacities to reach an elevation, say of six miles, and that both balloonists have balloons that will contain each 100,000 cubic feet of coal gas, and that they each take up one person, so that the weight of their respective balloons, each having to raise two persons, will altogether be 1,000 pounds for A’s and the same for B’s machine.
A’s balloon is to be quite filled with gas that lifts forty pounds the 1,000 feet, but B’s balloon is to be only half filled.