Chap. 5.] Hail. 487 



very (lowly. Its great furface alfo renders it very fuf- 

 ceptible of evaporation, which confiderably diminiihe& 

 its weight even in the coldeft weather. 



If the cold is fo moderate, as to allow the particles 

 of water to unite into drops before congelation takes 

 place, particles of ice are produced, which are called 

 hail. The (ame thing may be fuppofed to happen 

 when the lower regions of the atmofphere are colder 

 than the upper, which, though contrary to the general 

 courfe of things, fometimes happens. In fuch a cafe, 

 the aqueous particles, after having united above into 

 rain, are congealed in their defcent, and are con- 

 verted into hail. In the year 1775 or 1776, rain 

 fell at Liverpool, which became folid as loon as it 

 reached the furface of the earth, in fuch a manner as 

 to give a covering of ice to whatever was wet with 

 it, and even to form icicles on the drefs of perfons 

 expofed to it. This phenomenon I have alfo witnefied 

 elfewhere. 



Hail, when firft formed, muft be perfectly round, 

 becaufe formed from a fluid; and all fluids, when 

 placed in fuch fituations as to receive an equal pref- 

 fure in every direction from the medium which fur- 

 rounds them, naturally aflfume a fpherical form. Hail, 

 however, when it arrives at the earth is often angular ; 

 this mufl be explained, either by fuppofing that the 

 particles have begun to diflblve, or that they were fuf- 

 ficiently cold to congeal and attach to their (urface, 

 the aqueous particles with which they came. into con- 

 tact in their fall. Hail, when firft formed, is never 

 larger than the drops of water which fall in rain; 

 but from the caufe juft mentioned, hail-ilones have 

 fometimes been known to fall as large as nuts, or even 

 as hens' eggs. In order to convince ourfelves, that 

 fuch hail-ftones owe their extraordinary fize to the 

 I i' 4 additions 



