“The balloon is composed of silk, varnished with the liquid gum caoutchouc.  It is of vast dimensions, containing more than 40,000 cubic feet of gas; but as coal gas was employed in place of the more expensive and inconvenient hydrogen, the supporting power of the machine, when fully inflated, and immediately after inflation, is not more than about 2500 pounds.  The coal gas is not only much less costly, but is easily procured and managed.

“For its introduction into common use for purposes of aerostation, we are indebted to Mr. Charles Green.  Up to his discovery, the process of inflation was not only exceedingly expensive, but uncertain.  Two, and even three days, have frequently been wasted in futile attempts to procure a sufficiency of hydrogen to fill a balloon, from which it had great tendency to escape, owing to its extreme subtlety, and its affinity for the surrounding atmosphere.  In a balloon sufficiently perfect to retain its contents of coal-gas unaltered, in quantity or amount, for six months, an equal quantity of hydrogen could not be maintained in equal purity for six weeks.

“The supporting power being estimated at 2500 pounds, and the united weights of the party amounting only to about 1200, there was left a surplus of 1300, of which again 1200 was exhausted by ballast, arranged in bags of different sizes, with their respective weights marked upon them — by cordage, barometers, telescopes, barrels containing provision for a fortnight, water-casks, cloaks, carpet-bags, and various other indispensable matters, including a coffee-warmer, contrived for warming coffee by means of slack-lime, so as to dispense altogether with fire, if it should be judged prudent to do so.  All these articles, with the exception of the ballast, and a few trifles, were suspended from the hoop overhead.  The car is much smaller and lighter, in proportion, than the one appended to the model.  It is formed of a light wicker, and is wonderfully strong, for so frail looking a machine.  Its rim is about four feet deep.  The rudder is also very much larger, in proportion, than that of the model; and the screw is considerably smaller.  The balloon is furnished besides with a grapnel, and a guide-rope; which latter is of the most indispensable importance.  A few words, in explanation, will here be necessary for such of our readers as are not conversant with the details of aerostation.

“As soon as the balloon quits the earth, it is subjected to the influence of many circumstances tending to create a difference in its weight; augmenting or diminishing its ascending power.  For example, there may be a deposition of dew upon the silk, to the extent, even, of several hundred pounds; ballast has then to be thrown out, or the machine may descend.  This ballast being discarded, and a clear sunshine evaporating the dew, and at the same time expanding the gas in the silk, the whole will again rapidly ascend.  To check this ascent, the only recourse is, (or rather was, until Mr. Green’s invention of the guide-rope,) the permission of the escape of gas from the valve; but, in the loss of gas, is a proportionate general loss of ascending power; so that, in a comparatively brief period, the best-constructed balloon must necessarily exhaust all its resources, and come to the earth.  This was the great obstacle to voyages of length.