PHOSPHORESCENCE. 53 
enable us to walk without hesitation in any open 
country. 
Let the heavens be overcast, let the stars be 
hidden by an unbroken mass of clouds, and still a 
sufficiency of light will be diffused in the open 
country to prevent the difficulty and inconve- 
nience which would attend any attempt to walk 
in a dark cave, or in an apartment the shutters 
of which are closed. 
It appears to me that the atmosphere and the 
clouds themselves act in these cases like the 
phosphori spoken of in a previous chapter. Bemg 
exposed to the hight of the sun the whole day 
long, it 1s very probable that they emit a phos- 
phorescent light lke the Bologna stone, for in- 
stance, when the Sun’s rays are withdrawn from 
them; and moreover, that this phosphorescence 
may, in certain circumstances, assume an extra- 
ordinary intensity, as we shall see by some of the 
following examples. 
Here are the accounts by Rozier and Beccaria, 
alluded to above :— 
Rozier states that, being at Beziers, in France, 
on the loth August, 1781, at a quarter before 
eight in the evening, the sun haying gone down 
and the sky overcast, thunder was heard. At five 
minutes past eight, the storm having attained its 
height, Rozier observed a luminous point above 
the brow of a hill fronting his house; this point 
