2 3 o POPULAR LECTURES AND ADDRESSES. 



If they find that on one fine day it is negatively 

 electrified, the result will be valuable to science ; 

 and if on several days it is found to be all day 

 and all night negatively electrified, then there will 

 be a very great accession to our knowledge re- 

 garding atmospheric electricity. 



When I say the surface of the earth is negatively 

 electrified, I make a statement which I believe 

 was clue originally to Peltier. The more common 

 form of statement is that the air is positively 

 electrified, but this form of statement is apt to 

 be delusive. More than that, it is most delusive 

 in many published treatises, both in books and 

 encyclopaedias, upon the subject. I have in my 

 mind one encyclopaedia in which, in the article 

 " Air, electricity of," it is said that the electricity 

 of the: air is positive, and increases in rising from 

 the ground. In the same encyclopaedia, in the 

 article " Electricity, atmospheric," it is stated 

 that the surface of the earth is negatively 

 electrified, and that the air in contact with 

 the earth, and for some height above the earth, 

 neral, negatively electrified. I do not say 



