an the Production of Dephlogijlicated Air. 1 1 ^ 
thread of glafs, commonly called fpun glafs, fuch as is ufed for 
making brufhes for cleaning jewels, and for making a kind of 
artificial feather frequently fold by tbe Jew pedlars. This 
fpun glafs is no other than common glafs drawn out, when 
hot, into an exceeding fine thread; which thread, in confe- 
quence of its extreme finenefs, retains its flexibility after it 
has grown cold. 
I made choice of this fubftance not only on account of its 
great furface, but alfo on account of the ftrong attradlion which 
is known to fubfift between glafs and air, and the impoflibility 
of its communicating any thing to the water. 
The relult of the experiment was, that the globe being ex- 
pofed in the fun, air-bubbles began almoft immediately to make 
their appearance upon the furface of the fpun glafs, and in 4 
hours -/oV °f a cubic inch of air was collected, which, 
proved with nitrous air, gave ia+jn=i,i 2 9 or 88; after 
which, not a fmgle air-bubble more was produced, though the 
globe was expofed a whole week in the window, during which 
time there were feveral very warm, fine, iunfhiny days. 
This experiment (hews evidently, that fomething more is 
wanting to the production of pure air by water, expofed in the 
fun, than merely a furface to which the air diflolved in the 
water can attach itfelf, in order to its making its efcape. 
The air furnifhed in this experiment was doubtlefs merely 
that with which the water ifluing from the earth was over* 
charged, and wdiich would have made its efcape' from the 
water, had the water, inftead of being expofed with the fpun 
glafs in the fun, been limply left for fome time expofed to the 
free air of the atmofphere. 
It appears, that this air, naturally exifling in fpring water, 
inftead of being dephlogiflicated, is fomething worfe than 
Vol. LXXVII. " Q common 
