ee ——_ se 
‘Description of an Eudiometer. 389>* 
tirely arbitrary; but those, which I employ, 
are each ten grains of mercury at 60° Faht. 
the whole tube containing 100 grains. It is 
some trouble to divide this tube; but, when 
once prepared, any number may, by its means, 
be easily graduated. The successive portions 
of mercury, used in dividing wider tubes, are 
measured by this, into which they are drawn, 
either by plunging it into a jar filled to suffi- 
cient height with that fluid, or by the action 
of the mouth. . 
_ The two figures in the plate, which remain 
to be described (fig. 1. and 2.) represent an 
apparatus, which I have found extremely 
useful for submitting various gases to the long 
continued action of electricity. The platina 
wires, for conveying the electric fluid, are 
inclosed in two short pieces of almost capil- 
lary tube 6 c, which are sealed round them, 
and then ground away so as to expose merely 
the points atd d. These tubes are hermeti- 
cally sealed into the small globe at 6 c, so 
that the points of the wires may be at a 
proper striking distance. The vessel may be 
filled with gas over mercury, and closed by 
the stopper g, fig. 2, or the elongated stopper 
¢, fig. 1. But if it is desirable entirely to 
