PRESIDENTIAL ADDRESS, S.T.E. 1874. 233 



foundation is this assertion made ? Simply by 

 observation. It js a matter of fact ; it is not a 

 matter of speculation. I find that the air which 

 is drawn into a room from the outside on a fine 

 day is negatively electrified. I believe the same 

 phenomena will be observed in this city as in the 

 old buildings of the University of Glasgow, in 

 the middle of a very densely-peopled and smoky 

 part of Glasgow ; and therefore I doubt not that 

 when air is drawn into this room from the outside, 

 and a water-dropping collector is placed in the 

 centre of the room, or a few feet above the floor, 

 and put in connection with a sufficiently delicate 

 electrometer, it will indicate negative electrification. 

 Take an electric machine ; place a spirit-lamp on 

 its prime conductor ; turn the machine for a time : 

 take an umbrella, and agitate the air with it till 

 the whole is well mixed up ; and keep turning 

 the machine, with the spirit-lamp burning on its 

 prime conductor. Then apply your electric test, 

 and you will find the air positively electrified. 

 Again Let two rooms, with a door and passage 

 between them, be used for the experiment. First 



