( 19 ) 
Clouds, we muft only confider; whether that De- 
gree of Heat, which is known to rarefy Water 
14000 * Times, being compared with feveral of thofc 
Degrees of Heat in Summer, Autumn and Winter, 
which are capable of raifing Exhalations from Wa- 
ter or Ice ; the Rarity of the Vapours ( eftimated by 
the Degree of Heat) will appear to be fuch, that 
the Vapour will rife high enough in Winter, and 
not too high in Summer, to agree with the known 
^hanomena. 
That the Ejfedis are adequate to the Caufes m 
this Cafe, I think I can make out in the following 
Manner, viz. 
The Heat of boiling Water, according to Sir Ifaac 
Table ( Thil. TranfaSl. Num. x;o) is 34, 
the mean Heat of Summer 5', the mean Heat of 
Spring or Autumn 3, and the leall Degree of Heat, 
ac which Vapours life in Winter (^alias the mean 
Heat of Winter) is x. The Rarity of Vapour pro- 
portionable to thefe four Degrees of Heat, is 14000, 
205'8, 1135, and 82.3. The Rarity of Air is, in Sum- 
mer 900, in Spring or Autumn 85-0, and in Winter 
8co, the Denfiry of Water compared with the above- 
mentioned Denfities, being inverfely as One to thefaid 
fore-mentioned four Numbers. The Heights above the 
Earth to which the Vapours will rife, and at which 
they will be in aquilibrio, in an Air of the fame Den- 
fity with themfelves, will vary according to the Ra- 
rity of the Vapour depending on the Heat of the Sea- 
^ As the Bigrejfton wou'd be too long to mention here thofe Objervations on 
the 'Fire-Engine, which /hew that the Vapour from boiling Water is expanded 
140C0 Times more than cold Water j / refer the Reader to the 6 th Seftion of 
OL^th Contemplation o/Niewentyt’; Religious Philofopher, where he proves 
by an Experiment made with an JEolipile, that one Inch of 'Water produces 
1336s Inches of Vaj>ouri which, conjidering the great Allowances made a- 
gainjl the AJfertion, may well be call'd 14000, 
.P 2 
fbn. 
