PART II.

PRACTICE OF AEROSTATION.

CHAPTER I.

General Principles of Aerojlation.

HE whole earth, together with all

JL the bodies that are upon it, is sur-rounded by an invisible fluid called air;which has weight, and also elasticity, viz.may be easily compressed. Invert a commonwine glass, and, in that inverted situation,let it down into a bason of water; and itwill be found that the water cannot enterwithin the glass. That substance, which

prevents