Description of an Eudiometer. 387 
the purpose of receiving a graduated tube not 
differing from that of Dr. Hope, I employ 
a piece of tube of about + an inch diameter, 
and about one inch long. Into one end of this, f 
the graduated tube is accurately fitted by 
grinding; and the other end is made some- 
what funnel-shaped as shewn by Plate VI. 
fig. 3. 6. The outer surface of the wider tube 
being previously ground, to destroy its smooth- 
ness, the neck of the elastic bottle is firmly tied 
upon it, care being taken to bring the folds of 
string so low, that no space may he left for 
the lodgment of air between the bottle and 
the tube. ; 
The apparatus is used in a similar way to 
that of Dr. Hope, the gas being measured 
from time to time to ascertain when the ab- 
sorption ceases. The only difficulty, which 
is likely to be experienced, and which a little 
practice will overcome, is to return the whole 
of the gas from the bottle into the tube. Be- 
fore measuring the residuary gas, it is proper 
to remove the graduated tube from its attach- 
ment, either under water or mercury ; for: 
otherwise the elasticity of the sides of the 
bottle increases a little its apparent quantity. 
-In most cases, the graduated tube may 
be cylindrical as shewn by fig. 5; but when 
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