Mr. Read's Experiments and Observations, &c. s ey 
of its former electric charge, before 1 proceeded to accumulate 
another. 
Some observations which I made some time ago, induced 
me to suspect that air, by being vitiated even in a small de- 
gree in various ways, as by respiration, putrefaction, &c. lost 
a portion of its natural electricity, and became thereby elec- 
trified negatively : the following facts seem to substantiate 
this supposition. The room I usually inhabit being of small 
dimensions, is on that account more liable to suffer a change 
in the electrical state of its air than a larger one ; and having 
been often struck with the constancy of the doubler charging 
negatively in it, whereas in the open air, and often in the ad- 
joining room, which is larger, the doubler would give positive 
electricity ; I saw nothing to occasion this difference between 
the two rooms besides what could be attributed to the respira- 
tion and to the usual effluvium of my body. I was therefore 
curious to try on the 9 th of July, 1793, whether a change 
could be effected in the electrical state of the air in the large 
room by the same means. The weather being very hot and 
serene, therm. 75 0 , I invited a second person to sit with me in 
this room during the space of 20 or 30 minutes, with the 
door and windows close shut up ; I placed myself nearly in 
the middle, and my companion at the side of the room. At 
the end of 20 minutes I was in a profuse perspiration, which 
according to my ideas must promote the business in hand ; I 
therefore worked the doubler, and found the experiment 
to succeed agreeably to my expectation, as it now gave nega- 
tive electricity. 
Suspecting that similar effects must take place during sleep 
in my bed-room, which is on the north side of the house, I 
M m 2 
