The Writings of Benjamin Franklin. 153 



" does it gradually. 2. By breaking on it. 3. By making 

 " a smoke about it from burning wood. 4. By candle light, 

 " even though the candle is at a foot distance : these do it 

 " suddenly. — The light of a bright coal from a wood fire ; 

 " and the light of red hot iron do it likewise ; but not at so 

 " great a distance. Smoke from dry rosin dropt on hot 

 " iron, does not destroy the repellency ; but is attracted by 

 " both shot and cork ball,formingproportionable atmospheres 

 " round them, making them look beautifully, somewhat like 

 "some of the figures in Burnet's or Whiston's theory of 

 " the earth. 



" N.B. — This experiment should be made in a closet, 

 " where the air is very still, or it will be apt to fail. 



" The light of the sun thrown strongly on both cork and 

 " shot by a looking glass for a long time together, does not 

 " impair the repellency in the least. This difference between 

 " fire -light and sun light is another thing that seems new 

 " and extraordinary to us." 



Footnote : "This different effect probably did not arise from any difference 

 " in the light, but rather from the particles separated from the candle, being first 

 "attracted and then repelled, carrying off the electric matter with them ; and 

 "from the rarefying the air, between the glowing coal or red hot iron, and the 

 "electrified shot, through which rarified air the electric fluid could more 

 ' ' readily pass. " 



It will be noticed that Franklin was the discoverer of 

 the action of flames, as well as of the discharging 

 properties of red hot iron, which seem to have been 

 forgotten until re-discovered by Guthrie, in 1873 {Phil. Mag. 

 XLVL, p. 257). 



Another matter of interest is the experiment intended 

 to try the action of sunlight. Had Franklin used a clean 

 piece of zinc instead of iron shot he might have anticipated 

 Hertz's discovery of the action of strong light on the 

 discharge of gases. 



Franklin gives in one of the letters the first mention in 

 his note book of the line of thought which led him to the 

 invention of the lightning conductor. 



