CHAP. IV. 



AEROSTATION, INCLUDING THE PRINCIPLES, HISTORY, 

 AND MANAGEMENT OF BALLOONS. 



SECTION I. 

 Principles of Aerostation. 



1 HE fundamental principles of this art have been long and gene- 

 rally known, as well as the speculations on the theory of it j but 

 the successful application of them to practice seems to be altoge- 

 ther a modern discovery. These principles chiefly respect the 

 weight or pressure, and elasticity of the air, with its specific gra- 

 vity, and that of the other bodies to be raised or floated in it ; the 

 particular detail of which principles, however, we have not 

 space to enlarge upon. Suffice it therefore, for the present, to 

 observe, that any body which is specifically, or bulk for bulk, lighter 

 than the atmosphere, or air encompassing the earth, will be buoyed 

 up by it, and ascend, like as wood, or a cork, or a blown bladder, 

 ascends in water. And thus the body would continue to ascend to 

 the top of the atmosphere, if the air were every where of the same 

 density as at the surface of the earth. But as the air is compressible 

 and elastic, its density decreases continually in ascending, on ac- 

 count of the diminished pressure of the superincumbent air, at the 

 higher elevations above the earth ; and therefore the body will as- 

 cend only to such a height where the air is of the same specific 

 gravity with itself; where the body will float, and move along with 

 the wind or current of air, which it may meet with at that height. 

 This body then is an aerostatic machine, of whatever form or na- 

 ture it may be. And an air-balloon is a body of this kind, the 

 whole mass of which, including its covering and contents, and the 

 weights annexed to it, is of less weight than the same bulk of air in 

 which it rises. We know of no solid bodies, however, that are light 

 enough thus to ascend and float in the atmosphere ; and therefore 

 recourse must be had to some fluid or aeriform substance. Among 

 these, that which is called inflammable air, the hydrogen gas of the 

 new nomenclature, is the most proper of any that have hitherto been 



