People of Science: Benjamin Franklin

The Royal Society

Benjamin Franklin (1705-1790) 
Benjamin Franklin is now remembered as a Founding Father of the United States of America. However, his contemporaries knew him as a polymath: a prolific inventor, a political thinker and a scientist. His contribution to science was recognised by the Royal Society and is visible in our archival collections. 
Franklin: science communicator
Throughout his life, Franklin played a crucial role in disseminating scientific ideas. His diplomatic missions and trade-related travels led him from Philadelphia to London and Paris which allowed him to forge a powerful network of correspondents including the Royal Society. Here, Franklin records the succesful flight of a hot air balloon in Paris for the Royal Society. 

On 27 August 1783, Franklin attended the successful flight of a hot-air balloon in Paris. The attempt followed the invention of the 'globe aérostatique' by the Montgolfier brothers. He relayed promptly the information to the Royal Society.

Balloons were inflated by hydrogen produced by the reaction of sulphuric acid and iron.

Franklin: experimenter
Franklin's most famous contribution to science is the Philadelphia kite experiment. In the 1750s, the nature of electricity was not yet clearly understood and harnessing its power was a scientific ambition rather than a reality. Franklin - who was the first to conclude that the early condensers called 'Leyden jars' were storing electricity in glass - set out in 1752 to test his hypothesis that lightning was indeed electricity and observe its effects. 

In this letter to the botanist Peter Collinson FRS (1694-1768), Franklin describes the experiment details, the purpose of the experiment was:
1) To confirm that lightning was an electrical event
2) That a kite could conduct electricity
3) To test the effects of electricity on metal and man

Franklin refers to his previous successful attempt to 'draw the electric fire from clouds by means of pointed rods of iron erected on high buildings'. This described the Franklin rods.

Franklin goes on to recommend that the string of the kite be kept indoors, to prevent it from being wet and away from surfaces.

This description contradicts the mythical representation of Franklin and his son outdoors.

Franklin's experiments with electricity brought him an unprecedented popularity, as well as recognition from his peers.

The kite experiment became legendary and captured the imagination of the public. It is pictured here as the cover of a popular XIXth-century science book.

Franklin also experimented in other scientific fields such as chemistry. In this letter, he contemplates the effect of oil on water testing the theory supported by Roman seamen that it calms waves.

'The Learned too, are apt to slight too much the Knowledge of the Vulgar', he writes reminding readers of the humility necessary to scientific endeavours.

Franklin: inventor
Franklin is celebrated for his inventions. These technical drawings layout the construction of the 'Franklin stove', a metal fireplace reducing the amount of smoke coming from chimneys and increasing the heat retained in the room through the use of baffles.

Benjamin Franklin is credited with the invention of bifocals. Although the term was coined much later, Franklin indeed designed glasses for close-reading and to correct short-sightedness.

Bifocals were designed with a lower half of the glass more convex than the top, thereby aiding with reading and close observation through the bottom and seeing in the distance through the top-half.

Franklin: Fellow of the Royal Society
In recognition of his 'various discoveries in natural philosophy' and for being the 'first who suggested the experiments to prove the analogy between lightning and electricty', Franklin was elected FRS in 1756. 

Franklin's correspondence with Royal Society Fellows touches on a variety of subjects. This 'magic circle' is a beautiful example of mathematical constructions by Franklin.

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