[ •» J 
XXXVIII. 
The Elaftitity in the Air indeed, or in Water 
agitated by Fire, or in all the Exhalations proceed- 
ing from the Earth, arifes from the Principle of 
Repulfion only 5 for the Particles of Vapours, Exha- 
lations, and Air, ftand at a Diftance from one m- 
other, and endeavour to recede as far from one an- 
other as the Preffure of the incumbent Atmofphere 
will admit them. No Power yet known is able 
to comprefs the Air-Particles within the Sphere of 
their Attraction towards each other, fo as to deftroy 
their eiaftic Property > and yet Angle primary Parti- 
cles of Air are continually attracted by other Bodies, 
and consolidated with them, till by the ACtion of 
Fire, or Fermentation, they are feparated again, and 
reftored to their repulfive State. 
XXXIX. 
Hence we may obferve, that Elafticity, in differ- 
ent kinds of Things, or in Matter differently mode- 
lled, may arife from two feveral Caufes, viz . At- 
traction and Repulfion } and perhaps, in many In- 
fiances, from the Influence of both at one and the 
fame time. 
XL. 
Whenever any kind of Matter is a&uated by Fire, 
by Fermentation, or diffolved by any Menftruum, fo 
as to throw off its Particles in fubtile Vapour, there 
will 
