116 W. Gibbs—Analytical Notices. 
with great advantage to give a continued supply of air, and 
when the proper proportions of air and gas are obtained—which 
requires but an instant—the little tongues of blue fame remain 
constant for hours. A foot bellows may also be employed 
meniscus of porous I 
ware. In crucible ignitions, 12 
which a current of gas is passe 
Pry over the ignited substance—as 
pss for instance, in reducing metallic 
oe oxides in hydrogen—great care 
must be taken to prevent me 
chanical loss. In such cases I 
lace a porous capsule in the crucible above the substance 10 
eated, as in the figure. The gas may then be introduced 
through the perforated cover by means of a porcelain ig or 
the usual way, and passes through the porous capsule by . 
* Ring-burners with stands, and two rings of different diameters, may be had 
of Messrs. Rohrbeck & Goebeler, 4 Murray street, New York. 
