THE EARTH. 317 



fore, they will become too weighty for the air 

 which first raised them to sustain ; and they will 

 descend, with their excess of weight, either in 

 snow or rain. But, as they will fall precipitately 

 when they begin to descend, the air, in some 

 measure, will resist the falling ; for, as the des- 

 cending fluid gathers velocity in its precipitation, 

 the air will increase its resistance to it, and the 

 water will, therefore, be thus broken into rain ; 

 as we see that water which falls from the tops of 

 houses, though it begins in a spout, separates into 

 drops before it has got to the bottom. Were it 

 not for this happy interposition of the air between 

 us and the water falling from a considerable 

 height above us, a drop of rain might fall with 

 dangerous force, and a hailstone might strike us 

 with fatal rapidity. 



In this manner, evaporation is produced by 

 day ; but when the sun goes down, a part of that 

 vapour which his rays had excited, being no 

 longer broken, and attenuated by the reflecting 

 rays, it will become heavier than the air, even be- 

 fore it has reached the clouds ; and it will, there- 

 fore, fall back in dews, which differ only from 

 rain in descending before they have had time to 

 condense into a visible form. 



Hail, the Cartesians say, is a frozen cloud, half 

 melted and frozen again in its descent. A hoar 

 frost is but a frozen dew. Lightning we know to 

 be an electrical flash, produced by the opposition 

 of two clouds ; and thunder to be the sound pro- 

 ceeding from the same, continued by an echo re- 

 verberated among them. It would be to very 



