People of Science: Benjamin Franklin

By The Royal Society

People of Science with Brian Cox - Bill Bryson (2018-02-12) by The Royal SocietyThe Royal Society

Portrait of Benjamin Franklin (1782) by Joseph Wright (1756-1793)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. 

Paper by Benjamin Franklin describing a hot-air balloon demonstration in Paris Paper by Benjamin Franklin describing a hot-air balloon demonstration in Paris (1783) by Benjamin Franklin (1706-1790)The Royal Society

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. 

Filling a balloon with hydrogen gas, plate 3 from the book 'Description des experiences de la machine aerostatique de MM.de Montgolfier', by Faujas de Saint-Fond (Paris, 1783). (1783) by Barthelemy Faujas de Saint-Fond (1741-1819)The Royal Society

The Montgolfier brothers invented and demonstrated hot air balloons around 1782-1783.

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

Paper by Benjamin Franklin describing a hot-air balloon demonstration in ParisThe 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.

Paper by Benjamin Franklin describing a hot-air balloon demonstration in ParisThe Royal Society

Franklin was a key correspondent to the Royal Society, sending scientific news from Paris and Philadelphia.

Title page of 'A Letter from Mr. Franklin to Mr. Peter Collinson, F.R.S. concerning the Effects of Lightning.' (1751) by Benjamin Franklin (1706-1790)The Royal Society

Some of these letters were published in the journal of the Royal Society, The Philosophical Transactions.

Benjamin Franklin Drawing Electricity from the Sky (c. 1816) by Benjamin West, English (born America), 1738 - 1820Philadelphia Museum of Art

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. 

The Philadelphia Kite Experiment by Benjamin Franklin The Philadelphia Kite Experiment by Benjamin Franklin (1752) by Benjamin Franklin (1706-1790)The Royal Society

  In this letter to the botanist Peter Collinson FRS (1694-1768), Franklin describes the experiment details, the purpose of the experiment was:

The Philadelphia Kite Experiment by Benjamin FranklinThe Royal Society

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 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 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.

Cover of A Short History of Natural Science (1888) by Arabella Buckley (1840-1929)The Royal Society

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.

Stilling the Waters paper by Benjamin Franklin (1773-11-07) by Benjamin Franklin (1706-1790)The Royal Society

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.

Design for a stove by Benjamin Franklin by Benjamin Franklin (1706-1790)The Royal Society

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 (1767) by David MartinThe White House

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.

By Ted ThaiLIFE Photo Collection

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.

Royal Society Fellowship election certificate for Benjamin Franklin (1756) by The Royal SocietyThe Royal Society

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. 

Facsimile of a Letter from Benjamin Franklin at Craven Street London to Mr Canton in the possession of R Canton Esq at 22 and 23 Aldersgate Street Facsimile of a Letter from Benjamin Franklin at Craven Street London to Mr Canton in the possession of R Canton Esq at 22 and 23 Aldersgate Street (1765-05-29) by Benjamin Franklin (1706-1790)The Royal Society

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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