92 
Sir BenjamiK Thompson’s Experiments 
Experiment N c 4. 
Finding by the laft experiment (N° 3.) that heat alone, 
without light, was not fufficient to enable filk in water to pro- 
duce air, 1 was delirous of feeing the effeCt of light, without 
heat, upon them. To this end, I took the globe B, with its 
contents, and plunging it into a mixture of ice and water 
brought it to the temperature of about 50° F. and taking 
it out of this mixture, and expofing it immediately in the 
fun’s rays (which were very piercing at the time) I enter- 
tained it in this temperature above two hours by the occafional 
application of cloths, w T et in ice water, to the lower part of 
the globe. 
Notwithftanding this degree of cold, a confiderable quantity 
of air was produced ; though it was not furnifhed in fo great 
abundance as when the globe was buffered to become hot in the 
fun’s rays. 
Having thus afcertained the great effeCt of the fun’s rays m 
the production of the air furnifhed upon expofing filk in water to 
their influence, my next attempt was to determine, whether 
this arofe from any peculiar quality in the fun’s light ; on whe- 
ther other light would not produce the fame effeCt. With a 
view to afcertaining this point, which I conceived to be of 
very great importance, I made the following interefling expe- 
riment. 
Experi?nent N° 3. 
Having removed all the air from the globe B, and having 
fupplied its place with a quantity of frefh water, fo as to ren- 
der it quite full, I replaced it inverted in its jar, and removing 
it into a dark room, furrounded it with 6 lamps with reflectors, 
and 
