on the ProduSiion of Dephlogifticated Air > 95 
more fafs and convenient, a fmall ring, or hoop, of foft wood, 
was nailed down upon the board in that part. 
By this arrangement the jars were fpared, and the end of 
the neck of the globe being eafy to be come at,. by introducing 
a wire, or, what I commonly made ufe of in preference, a 
fmall glafs tube, into the globe, the air hanging attached to the 
filk can at all times be feparated from it ; which is often necef- 
fary, in order to determine with greater precifion the quantity 
of air furnifhed in any given time. 
The air produced naturally rifes to that part of the globe 
which is uppermoft, where it collects in a body, driving out an 
equal volume of water ; which, to prevent its running about, 
may be collected, by placing a proper vefiel under the mouth, 
or end of the neck of the globe, to receive it. 
The method of removing the air from the globe is too well 
known to require a defcription. I would however obferve, 
that in doing it care fhould be taken, that the water in which 
the globe is immerfed be quite clean, and of the fame kind with 
that in the globe, otherwife that which enters the globe, to 
replace the air removed, might derange the experiment. 
Having provided myfelf with a number , of globes of dif- 
ferent fizes, all fitted with boards or Hands to fupport them, 
in the manner above defcribed, I proceeded in the courfe of my 
experiments as follows. 
Finding that raw filk, expofed in water to the action of 
light, caufes the water to yield pure air in fo great abundance, 
1 was defirous of finding out whether this arofe from any pecu- 
liar quality poffeffed by the filk ; or whether other bodies might 
not be made to produce the fame effect : to this end, having 
provided 6 globes, each about inches in diameter, and 
having filled them with frefh lpring-water, I introduced into 
them 
