424 PHILOSOPHICAL TRANSACTIONS. [aNNO 1794. 



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°, I invited a 2d 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 pro- 

 mote the business in hand ; I therefore worked the doubler, and found the 

 experiment to succeed agreeably to my expectation, as it now gave negative 

 electricity. 



Suspecting that similar effects must take place during sleep in my bed-room, 

 which is on the north side of the house, I examined the electric state of the air 

 both within and without the bed-room a little before I went to rest, and found it 

 positive by the doubler. I arose at six o'clock next morning, and worked the 

 doubler, and it quickly became electrified negatively. But as it often happens, 

 in completing one discovery we get an imperfect knowledge of others, I was 

 surprized to observe, by the action of the doubler, to what a great degree the 

 air in the room was deprived of its insulating quality ; for though the doubler 

 accumulated electricity in every revolution strong enough to enable me to ascer- 

 tain its kind, yet its electric charge was conducted away almost as quickly as 

 obtained. 



With a view to determine what happens in the upper part of the house, I 

 went up into the garret, and found it close shut up, and the air within it was 

 excessively hot, and in some degree noxious ; therm. 80°. After a very few 

 turns of the revolving plate, the doubler became electrified negatively : I imme- 

 diately set the door and windows wide open, and another door which opens over a 

 bow window, to let in fresh air ; but the wind blowing moderately strong from 

 the east, and tlie bow window door being at the north end, and the windows at 

 the south end of the garret, made it unfavourable for an east wind to drive 

 through it, therefore its electric state remained the same in kind after they had 

 been opened, as when shut ; for I examined it at several intervals of time : yet 

 the state of the air became thereby considerably better to breathe in. These 

 facts will appear still more extraordinary, when we consider that the general 

 state of atmospheric electricity at the time of performing these experiments was 

 of the positive kind, as appeared by the doubler when placed on the wooden 

 hand-rail of the bow window, which is only 3 feet Q inches out of the garret. 

 Had the direction of the wind been north or south, it would have passed through 

 the garret with force, and would, no doubt, have changed by regular gradation 

 its electricity to positive ; a fact that I have often observed to succeed very 

 quickly. 



I also observed, that when the excessive heat of the sun was full on any other 



