[ 4«7 ] 
to the circumambient Atmofphere, and dilfipated as 
faft as excited. 
This Theory has been confirmed to me by divers 
Experiments, but by none more remarkably than on 
the Evening of the Day I made thofe before-men- 
tion’d ; when the Vapours, which in the Afternoon, 
by the Sun’s Heat, and a brisk Gale, were dillipated, 
and the Air perfe&ly dry, defeended again in great 
Plenty, upon the Abfence of both, and in the Even- 
ing was very damp. For between feven and eight 
o’ Clock, 1 attempted again the fame Experiments in 
the fame manner, without being able to make any 
of them fucceed ; though all thofe mentioned in 
this Paper, with others of lefs Note, were made in 
lefs than half an Hour’s time. 
I am the more particular in this, being willing 
to fave the Labour of thofe, who are defirous of 
making this Kind of Trials. For, although fome 
of the lelfer Experiments may fucceed almoft at any 
time, yet I never could find, that the more remark- 
able ones would fucceed but in dry Weather. Iam, 
Gentlemen , 
Tour moft obedient , 
London* -April 25 . 
1745. Humble Servant , 
W. Watfo n. 
TIL. A 
