uncommon Darkneft, on May 19, 1780. 243 
» Having mentioned the phenomena, with fuch obfervations 
upon them, as I have been able to collect, I hall now endea- 
vour to account for the cauíe of this unuíual appearance. 
From the obfervations that have been mentioned, we may 
conclude with much certainty, that the atmofphere, on the 
19th of May, was charged with an uncommon quantity of va- 
pour. That this was the cafe, is evident from the large quana 
tity of fmoke and vapour that appeared i in the atmofphere for 
feveral days before ; which was fo great, as to darken the fun 
and moon,and render all objects, at adiftance, of a dull and very 
hazy appearance. It was alfo evident, from the defcent of thofe 
large quantities of foot, or black athes, which, through a long 
extent of country, were found mingled with the rain that fell, 
and floating on the furface of the waters. And the caufe from 
whence the uncommon quantity of thefe vapours was derived, 
is eafily afcertained. It is well known, that in this part of 
America, it is cuftomary to make large fires in the woods, for 
the purpofe of clearing the lands in the new fettlements. This 
was the cafe this fpring, in a much greater degree than is com- 
mon. In the dus of Yor£, in ELM SU Pon of the ftate 
ias andi in : 
up. The SET in ae new towns is ad been i in jid 
ing up their lands this way, for two or three weeks before : and 
fome large and extenfive fires had raged in the woods for feve- 
ral days before they could be extinguifhed. In addition, there- 
fore, to what arifes from evaporation, and thofe exhalations 
- which are conftant and natural, a much larger quantity of va- * 
pour arofe from thofe large and numerous fires, which extended 
all around our frontiets.” As the weather had been clear, th f 
a G g E 
