358 Abbe fontana’s Experiments and 
tides of common and inflammable air, or dephlogifti- 
cated and inflammable air, are put into a tube, and two 
birds are introduced in it, fo that one of them may ftand 
at the top, and the other at the lower part of the inverted 
jar; it will be found, that the firft mentioned of thefe 
birds not only will die confiderably fooner than the 
other, but will fhew figns of unealinefs as foon as it is 
come to that place. 
The inflammable air, therefore, when breathed toge- 
ther with a conliderable quantity of common air, muft 
always fwim at the top of it, filling the cavity of the 
wind-pipe, &c. while the common air occupies the lower 
place, and filling the fmallefi: pulmonary veficles is fub- 
fervient to the ordinary funddions of the lungs. 
Here I put an end to my obfervations upon inflam- 
mable air confidered with refpe£t to refpiration; but I 
beg leave to add a few words refpedting a property of the 
inflammable air, which, as far as I know, has been over- 
looked by the moft diligent obfervers. 
I mean here to fpealc of fuch inflammable air as is ex- 
tracted from metals, by means of oil of vitriol, efpecially 
that extracted from iron and zinc. The air of thefe me- 
tals, when prefented to the flame of a candle, not only 
burns with a whitifh flame inclining to green (as is well 
known); but exhibits a kind of fparks or explofions 
which 
