{ 579 ) 
fing all its Excefs of Gravity above that of the VVater^ 
and the Water gaining it. 
Hence it follows, that a falling Oloud, when it 
comes to an uniform Morion, will not only add to the 
Weight of the Air as much as the Weight of an equal 
Bulk of Air; but even as much as its whole Weight 
amounts to, tho’ it be fpecifically heavier than the Air 
about it. 
All the Diminution of Weight that can be allow’d in 
this Cafe is this. If we imagine the Air to have a 
fmooth, regular Surface, as we have at firft flippos’d, for 
if that be not allow’d, we may take any imaginary Sur- 
face of it above the Clouds) when a falling Cloud is 
diminilh’d in Bulk, (as when ic is chang’d into Rain j 
the Surface of the Air will fubfide in proportion to that 
diminution, and therefore will weigh lefs, by lb much 
as is the Weight of a Quantity of Air equal to the Bulk- 
that Cloud has loft: But when the Drops of Rain after* 
their Acceleration (occafion’d by their Excefs of Gra- 
vity above that of the Air^ are come to an uniform^ 
Motion by the Refiftance of the Air, they reftore ro the 
Air the Weight that it had loft. Now this uniforns' 
Motion being acquir’d in about two Seconds of Time, 
and the Diminution of Gravity in the Air being infen- 
fible, when compared to near three Inches of Mercury 
ffor fuch is the Variation of the Barometer with us) can ^ 
no way be the Occafion of thofefofenfible Alterations iiii 
it, which happeaforae time before Rain or Fair Weather. 
Add to this that the vphole ^antitj of Rain that falls in 
England and Vtuncc, in the Space of one Tear, [cares 
ever equals tm Inches yf Mercury s And in moji t laces^- 
between the Tropicks, the Rains fall, at certain Seafons,. 
in very great ^anilties, and yet the jhervs - 
there very little or no Alteration^ 
