8 Ittature'e /RMracles. 



true of many of the more important develop- 

 ments in the science and applications of 

 electricity during the last twenty-five or thirty 

 years. 



Following Hawksbee may be mentioned 

 Stephen Gray, Sir Isaac Newton, Dr. Wall, 

 M. Dupay and others. Dupay discovered the 

 two conditions of electrical excitation known 

 now as positive and negative conditions. In 

 1745 the Leydt-ii jar was invented. It takes 

 its name from the city of Leydcu, win -re its 

 use was first discovered. It is a glass jar, 

 coated inside and out with tin-foil. The in- 

 side coating is connected with a brass knob at 

 the top, through which it can be charged with 

 electricity. The inner and outer coatings 

 must not be continuous but insulated from 

 each other. The author's name is not known, 

 but it is said that three different persons in- 

 vented it independently, to wit, a monk by the 

 name of Kleist, a man by the name of Cuneus, 

 and % Professsor Muschenbroeck of Ley den. 

 This was an important invention, as it was 

 the forerunner of our own Franklin's dis- 

 coveries and a necessary part of his outfit with 

 which he established the identity of lightning 

 and electricity. Every American schoolboy 

 has heard, from Fourth of July orations, how 

 " Franklin caught the forked lightning from 

 the clouds and tamed it and made it sub- 

 servient to the will of man." How my boyish 



