[ z 47 ] 
decreafeof bulk; and as I have alfo kept fome for a 
few days, in bottles inverted into vcffels of fope leys 
and fpirit of fal ammoniac, without perceiving their 
bulk to be at all diminifhed. 
Jt has been obferved by others, that, when a piece 
of lighted paper is applied to the mouth of a bottle, 
containing a mixture of inflammable and common air, 
the air takes fire, and goes off with an explofion. In 
order to obferve in what manner the effect varies 
according to the different proportions in which they 
are mixed, the following experiment was made. 
Some of the inflammable air, produced by difl'olving 
zinc in diluted oil of vitriol, was mixed with com- 
mon air in feveral different proportions, and the in- 
flammability of thefe mixtures tried one after the other 
in this manner. A quart bottle was filled with one 
of thefe mixtures, in the manner reprefented in Fig. z. 
The bottle was then taken out of the water, fet up- 
right on a table, and the flame of a lamp or piece of 
lighted paper applied to its mouth. But, in order to 
prevent the included air from mixing with the out- 
ward air, before the flame could be applied, the mouth 
of the bottle was covered, while under water, with a 
cap made of a piece of wood covered with a few 
folds oflinnen; which cap was not removed till the 
inftant that the flame was applied. The mixtures 
were all tried in the fame bottle ; and, as they were all 
ready prepared, before the inflammability of any of 
them was tried, the time elapfed between each trial 
was but fmall : by which means I was better able to 
compare the loudnefs of the found in each trial. The 
refult of the experiment is as follows. 
U 2 
With 
