3993. J 
ExpLaNATION of the Ficures. 
Fig. kh THE great meafure, or 
great glafs tube, in its fituation in 
_ the experiment of examining air, 
with the brafs fcale upon it, and 
the magnifier ftuck to the brats 
tube, on purpofe to adapt accurately 
the firit. mark of the {cale to the 
beginning of the column of air. 
The glafs tube is fufpended upon 
the two brafs rings or gingle (in 
the way the common {fea-compafles 
are fufpended) to keep it always in 
a perpendicular fituation. AAAA 
is the brafs tube full of water, in 
which the glafs tube fixed to the 
brafs meafure is fufpended. This 
brafs tube is reprefented tranfparent 
on purpofe to fee in what manner 
a: the 
