124 THE HISTORY OF SCIENCE 



recognized two sorts of electricity, obtained by rub- 

 bing a glass rod and a stick of resin, and had 

 spoken of them as vitreous and resinous. For Frank- 

 lin electricity was a single subtle fluid, and electrical 

 manifestations were owing to the degree of its pres- 

 ence, to interruption or restoration of equilibrium. 



His mind, however, was bent on the use, the ap- 

 plications, the inventions, to follow. He contrived 

 an " electric jack driven by two Ley den jars and 

 capable of carrying a large fowl with a motion fit 

 for roasting before a fire." He also succeeded in 

 driving an " automatic " wheel by electricity, but he 

 regretted not being able to turn his discoveries to 

 greater account. 



He thought later in 1748 that there were 

 many points of similarity between lightning and the 

 spark from a Leyden jar, and suggested an experi- 

 ment to test the identity of their natures. The sug- 

 gestion was acted upon at Marly in France. An iron 

 rod about forty feet long and sharp at the end was 

 placed upright in the hope of drawing electricity 

 from the storm-clouds. A man was instructed to 

 watch for storm-clouds, and to touch a brass wire, 

 attached to a glass bottle, to the rod. The conditions 

 seemed favorable May 10, 1752 ; sparks between 

 the wire and rod and a " sulphurous " odor were 

 perceived (the manifestations of wrath !). Franklin's 

 well-known kite experiment followed. In 1753 he 

 received from the Royal Society a medal for the 

 identification and control of the forces of lightning ; 

 subsequently he was elected Fellow, became a mem- 

 ber of the Academie des Sciences, and of other 

 learned bodies. By 1782 there were as many as four 



