376 Count RumforcFs Experiments. [Book V. 



It has fincc been obferved, that feveral animal lub- 

 ftances, as well as vegetables, have a power of fepa- 

 rating ck'phlogifticated air, or oxygen gas, from water, 

 when expofed to the action of the fun for a confider- 

 able time. 



The ingenious Count Rumford obferved, that raw filk 

 has a remarkable power of producing pure air from wa- 

 ter. He found, that by introducing thu tv grains of this 

 fubftance, firft wafhed in water, into a thin glals globe 

 four inches and a half in diameter, having a cylindrical 

 neck three- fourths of an inch wide and twelve inches 

 long, inverting the globe in a jar filled with the fame 

 kind of water, and expofmg it to the action of the fun 

 in the window, in lefs than ten minutes the filk be- 

 came covered with an infinite number of air bubbles, 

 gradually increafmg in fize, till at the end of two 

 hours the filk was buoyed up, by their means, to the 

 top of the water. They feparated themfdves by de- 

 grees, and formed a collection of air in the upper part 

 of the globe, which, when examined by the eftablifhed 

 teft, appeared to be very pure. In three days he col- 

 lected three an,d three-fourths of a cubic inch of pure air, 

 into which a wax taper being introduced, that had juft 

 before been blown out, the wick only remaining red, it 

 inftantly took fire, and burned with a bright and en- 

 larged flame. The water in the globe had acquired 

 the fmell of raw filk, it loft fomt thing of its tranlpa- 

 rency, and aflfumed a faint grcvhifh caft. 



It \vas obferved, that when this experiment was 

 made in the dark, only a few inconfiderab^e bubbles 

 were formed, which remained attached to the filk -, nor 

 \vas it otherwife when the glafs globe was removed 

 into a German (love. In the latter cafe, indeed, fome 

 (ingle bubbles had detached themfelves from the filk^ 



and 



