LESSONS IN ELECTRICITY. 



820 



Fio. 54. 



ling and light of the electric spark, and 

 thunder and lightning. The greatest in- 

 vestigator in this field is the celebrated 

 Dr. Franklin. He made an exhaustive 

 comparison of the effects of electricity 

 and those of lightning. The lightning 

 flash he saw was of the same shape as the 

 elongated electric spark ; like electricity, 

 lightning strikes pointed objects in pref- 

 erence to others ; lightning pursues the 

 path of least resistance ; it burns, dis- 

 solves metals, rends bodies asunder, and 

 strikes men blind. Franklin imitated all 

 these effects, striking a pigeon blind, and 

 killing a hen and turkey by the electrical 

 discharge. I place before you in fig. 

 - ? -, with a view to its comparison with a 

 ;*charge of forked lightning, the long 

 spark obtained from an effective ebonite 

 machine, furnished with a conductor of a 

 special construction, which favors length 

 of spark. 



Having completely satisfied his mind 

 by this comparison of the identity of 

 both agents, Franklin proposed to draw 

 electricity from the clouds by a pointed 

 rod erected oa a high tower. But be- 

 fore the tower could be built he succeed- 

 ed in his object by means of a kite with 

 a pointed wire attached to it. The 

 electricity descended by the hempen 

 string which held the kite, to a key at 

 the end of it, the key being separated 

 from the observer by a silken string held 

 in the hand. Franklin thus obtained 

 sparks, and charged a Leyden phial with 

 atmospheric electricity. 



But, spurred by Franklin's researches, 

 an observer in France had previously 

 proved the electrical character of light- 

 ning. A translation of Franklin's writ- 

 ings on the subject fell into the hands of 

 the naturalist Buffon, who requested his 

 friend D'Alibard to revise the transla- 

 tion. D'Alibard was thus induced to 

 erect an iron rod 40 feet long, supported 

 by silk strings, and ending in a" sen try- 



box. It was watched by an old dragoon 

 named Coiffier, who on the 10th of May, 

 1752, heard a clap of thunder, and im- 

 mediately afterwards drew sparks from 

 the end ot the iron rod. 



The danger of experiments with metal 

 rods was soon illustrated. Professor 

 Richmann of St. Petersburg had a rod 

 raised three or four feet above the tiles 

 of his house. It was connected by a 

 chain with another rod in his room ; the 

 latter rod resting in a glass vessel, and 

 being therefore insulated from the earth. 

 On the Gth of August, 1753, a thunder 

 cloud discharged itself against the exter- 

 nal rod ; the electricity passed down- 

 wards along the chain ; on reaching the 

 tod below, it was stopped by the glass 

 vessel, darted to Richmann's head, which 

 was about a foot distant, and killed him 

 on the spot. Had a perfect communica- 

 tion eiisted between the lower rod and 

 the earth, the lightning in this case would 

 hav expended itself harmlessly. 



In 1749 Franklin proposed lightning 

 conductors. He repeated his recom- 

 mendation in 1753. He was opposed on 

 two grounds. The Abbe Nollct, and 

 those who thought with him, considered 

 it as impious to ward off heaven's light- 

 nings, as for a child to ward off the 

 chastening of its father. Others thought 

 that the conductors would " invite" the 

 lightning to break upon them. A long 

 discussion was also carried on as to 

 whether the conductors should be blunt 

 or pointed. Wilson advocated blunc 

 conductors against Franklin, Cavendish, 

 and Watson. lie so influenced George 

 III., hinting that the points were a re- 

 publican device to injure his Majesty, 

 that the pointed conductors on Bucking- 

 ham House were changed for others end- 

 ing in balls. Experience of the most 

 varied kind has justified the employment 

 of pointed conductors. In 1769 St. 



