{ .a79 -3 
degree compofed of the methods 
ufed by the two moft eminent phi- 
lofophers in this branch of natural 
knowledge, the Rev. Dr. Pricttley, 
and Abbé Fontana. It is this: I 
let up in the little meafure as much 
common air as will fill it; after 
which, I take hold of its brafs 
flider, and keep it under water ex- 
actly 15 feconds, when I lift it up 
pi the brafs dlider. be: on .a_ level 
with the water of the trough, and 
| mare the fcr & to cne Mf the column 
of air within the meafure ; ; I then 
invert the. meafure under water, to 
let out all the air which was re- 
maining under the flider. I let up 
immediately this meafure of air in 
the large tube, and fill the little 
meafure in the fame manner with 
nitrous air newly made from. red 
copper, in the manner explained” Pp. 
1a Peed +4 
e~ _ 
