O n 
OF CORNWALL. 
ceffive ^ e g iee Reparation, rife in the air in proportion to their 
hghtnefs, the heavier air forcing the rarefied fluid to afcend into the 
Atmofphere till it finds a place where it refls in equilibrium amono- 
bodies of equal lightnefs to itfelf. This feparation or comminution 
■ k ; ^° ta ^ ^ ^ ater kma RR parcels, may be performed 
either by collifion againft harder and more compact bodies, or by 
heat. I he firft we often fee performed at the bottom of Cafcades, 
where the Water that falls but a few fathoms, {hall rife in a miff 
-from the bottom where it is broke ; and there are inflances of clouds 
* _ llj g k om tkc Aff °f Waters which may be feen five miles off h . Col- 
liion will therefore excite vapours; but that which is more conffantly 
producing this effedt in every part of the univeife, is Heat; whether 
from the Sun, which is always bufy this way, or from artificial 
ignition, or that generally invifible elemental fire which is diftributed 
t rougi a matter. It has been by many Naturalifts imagined, that 
Teat raifes vapours by extending the air inclofed in the pores of 
Water, and forming gradually a thin film or bubble of Water of 
luch dimenfions that it becomes greatly lighter than the fame {pace 
of common air and therefore rifes above it : but this fuppohtion is 
not tenable ; for it is obferved, that fleam will rife in the receiver 
of an air-pump, where, though there remains fome air, there is 
not enough to conftitute fuch a procefs. It may here alfo be added, 
that earth and ftones and metals may be raifed into the Atmof- 
phere, although their parts will not form bubbles as thofe of 
a er wi . As this too generally allowed fuppofition is not to be 
Supported when Aridity examined, fo neither is it at all neceffaiy 
ior ns to conuder m this cafe any other than the divifibility of 
Water, and the mfinuating and difperfive qualities of fire ; both 
^ ^. their e &' C( ^ s - Fitej we fee, feparates more or lefs the parts 
r -° le ^ whether fluid or folid, and makes them rife in the air: 
lAw'A is al1 that needs be fu PP° fed ; fire does no 
rates if t r an „ to ad otber bodies under its power : it fepa- 
1 « ” ° U J 1 ™ a P ort ‘ons, that the air is more ponderous than 
tne fleam, and of confequence remains nearer to the earth by its 
lupenour gravitation. J 
• 1 P ai [ S va P our are not all equally fmall, but fmall accord- 
tC> m j^ 1 C< 1 ° ^ eat ratifies them : they will rife in air, 
when ranfied only 800 times; but they will rife quicker, (that is, 
1 1 greater force) and higher, according to all the intermediate 
becor> eS ° rare ^J on ’ from 800 to 1400. Vapour greatly heated 
r rnrn CS °. elaftlck tkat k w iRR move vaft weights ; nay, it appears 
experiment, that, when it is fufficiently rarified, it exceeds 
Mufichenbr. page 740^ ^ ^* a ^ ara ' n North America, and that of the river Veiino in Italy, 
the 
