284 PRESSURE IN THE AIR, 



was shrivelled and fiacced, becomes round and 

 tense ; this effect was particularly noticed b^ 

 Mr. BALDWIN, in one of his aerial excursions ; 

 he found in his ascent, that some bladders, tied 

 up with small portions of air in them, crackled 

 and expanded very considerably. The fact is 

 proved, by what takes place in the balloon it- 

 self; although it appears near the surface of 

 the earth loose and flacced, in consequence of 

 not being so completely filled as it would ad- 

 mit; it is seen gradually to swell and to dilate, 

 when it ascends to high points of elevation, 

 insomuch, that if a portion of the air which it 

 contained, were not allowed to get out of it, by 

 means of an aperture, constructed for that pur- 

 pose ; such is the increased power of .expand- 

 ing which the air within has acquired, in con- 

 sequence of diminished resistance of the air 

 without, that it would burst the sides of the 

 balloon, and escape from its ^confinement ; as it 

 is found to do when it is confined in a glas 

 vessel, or bladder, under an exhausted re- 

 ceiver. 



The diminution of atmospheric pressure at 

 high points of elevation, w r as further proved by 

 SAUSSURK, in his ascent to the top of mount 

 Blanc ; not only by the great inconveniency 

 which he experienced in his own person, but 

 by the small report which a pistol fired in that 

 situation produced on his auditory nerves. 



