tncommon Darknefi, on May 19 ro 1786. 243 
duce all’ the phenomena | ‘that wete obferved Ma y19. 1780. T 
"Thus the direction in which the darknefs came on, ee 
termined by the direction of the wind ; which accordingly was ra 
ferved to be from the S.W. The degree of the darknefs would 
depend on the denfity, colour, and fitüation of the clouds and 
vapour ; and the manner in which they would tranfmit, 1 ett, 
refract, or abforb the rays. of light. "The extent “of m dark- 
nefs would be as great as the extent of the vapour : and the du- 
ration of it would continue until the gravity of the air became. 
{o altered, ‘that the vapours would change their ‘fituation, by an. 
afcent.-or defcent. -All which particulars will, I think, -be 
found to agree very exactly with the obíervations that have been. 
mentioned. Nor does the effe& of the vapours, in- darkening 
‘terreftrial objects, when dems! near the furface of the earth,. 
ppear to have been gr r thanit was in darkening the 
faf "anb moon, when (heit fituation was higher i in the atmof-. : 
phere. 
——À 
"Upon the whole, it is evident, ‘that. the. Ler aa was’ 
chara ina nies PNG with pesa s 
red : a variety of Emus aud pce ; and py ‘he. 
come weakens. shiarbed or fo far reflected, as not to fall up- 
1 objeéts on the earth in t he ufüal manner. And as » the dif- 
