The Lightning Rod, Positive and Negative Electricity - 1751
Benjamin Franklin (1706 - 1790)

Experiments and Observations is recognized as the premiere scientific work of the great Benjamin Franklin.  In it he develops the terms positive and negative, discusses the action of pointed conductors (i.e. the lightning rod), the use of lead as the inner coat of a Leyden jar, and describes in detail his famous kite experiment:

"Make a cross with two light strips of cedar, the arms so long as to reach the four corners of a large silk handkerchief when extended.  Tie the corners of the handkerchief to the extremities of the cross, so you have the body

of a kite which, being properly accommodated with a tail, loop and string, will rise in the air like those made of paper; but, this being made of silk, is better to bear the wet and wind of a thunder-gust without tearing.  To the top of the upright stick of the cross is to be fixed a very sharp-pointed wire, rising a foot or more above the wood.  In the end of the twine, next to the hand is to be held a silk ribbon, and where the silk and the twine join a key may be fastened.  This kite is to be raised when a thunder-gust appears to be coming on, and the person who holds the string must stand within a door or window, or under some cover, so that the silk ribbon may not be wet, and care must be taken that the twine does not touch the frame of the door or window.   As soon as any of the thunder clouds come over the kite, the pointed wire will draw the electrified fire from them,

and the kite with all the twine will be electrified, and the loose filaments of the twine will stand out every way and be attracted by an approaching finger.  And when the rain has wetted the kite so that it can conduct the electric fire freely, you will find it stream out plentifully from the key on the approach of your knuckle.  At this key the phial (Leyden jar) may be charged, and from the electric fire thus obtained spirits may be kindled, and all other electric experiments be performed which are usually done by the help of a rubber glass globe or tube, and thereby the sameness of the electric matter with that of lightning completely demonstrated."