$56 Mr Harvey’s Observations on the formation of Mists , 
When the atmosphere is completely saturated with vapour, 
the greatest quantity of dew will be deposited, when the land, 
by a free radiation to a pure and tranquil sky, has its tempera- 
ture diminished by the greatest possible quantity below that of 
the air reposing on its surface ; and a mist of the greatest de- 
gree of density will be formed, when the temperature of the 
adjacent water is above that of its superincumbent air, also by 
the greatest possible quantity. The temperatures of the two 
masses of air, although unequal, may therefore be regarded as 
occupying a kind of middle state between the extremes here 
alluded to. 
In all cases the density of a mist will be jointly proportional 
to the difference of temperature between the sea and land, and 
the quantity of vapour held in solution by the atmosphere at 
the time of its formation. 
To show, however, the quantities of moisture that will be 
precipitated in the form of mist, fog, or rain, from the mingling 
together of equal masses of perfectly saturated air, of different 
degrees of temperature, the following examples are given ; and 
from which it will be perceived, that the moisture deposited in- 
creases with the difference of temperature of the volumes of 
air. The temperatures are those of the centesimal scale ; and 
the grains of vapour are what a metrical cube of air contains 
at the respective temperatures, when in a state of saturation, 
according to the experiments of Professor Leslie. 
Grains of Vapour 
Grains of Vapour 
dissolved in a 
dissolved in a 
Grains of Vapour 
1 
metrical cube of 
Means of the 
metrical cube of 
deposited in the 
Air, at the re- 
preceding. 
Air, at the means 
form of Mist, 
s 
spective Tempe- 
of the respective 
Fog, or Rain. 
a> 
H 
ratures. 
Temperatures. 
4° 
6 
120.3 
132.0 
126.1 
126.0 
0.1 
4 
8 
120.3 
144.T 
132.5 
132.0 
0.5 
4 
10 
120.3 
158.7 
139.5 
138.2 
1.3 
4 
12 
120-3 
174.1 
147.2 
144.7 
2.5 
4 
14 
120.3 
191.0 
155.6 
151 6 
4.0 
4 
16 
120.3 
209.5 
164.9 
158.7 
62 
4 
18 
120.3 
229.7 
175.0 
166.2 
8.8 
4 i 
20 ! 
120.3 
252.0 
186.1 
174.1 
12.0 
