This portrait, which depicts Franklin as a learned scientist and inventor, was one of his favorites. Pictured on the left is the signal-bell apparatus Franklin devised to detect the presence of electrically-charged clouds. The bolt of lightning , seen through the open window, became an attribute closely identified with Franklin. At Franklin's death French philosopher/scientist Jacques Turgot wrote: “He seized the lightning from the sky and the scepter from the hand of tyrants.”
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The Franklin Stove
Franklin wrote this description of the stove he had invented to promote sales of a model being manufactured by his friend Robert Grace. A series of partitioned iron plates permits a continuous supply of fresh warm air, separated from the smoke, to be distributed equally throughout the room. By controlling the airflow, less heat is lost, and much less wood is needed. Franklin's stove became so popular in England and Europe that this essay was frequently reprinted and translated into several foreign languages.
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Benjamin Franklin is credited with the invention of bifocal glasses, which he sketched here for his friend George Whatley, a London merchant and pamphleteer. Franklin told Whately he found them particularly useful at dinner in France, where he could see the food he was eating and watch the facial expressions of those seated at the table with him, which helped interpret the words being said. He wrote: “I understand French better by the help of my Spectacles.”
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Experiments in Electricity
In 1751, Peter Collinson, President of the Royal Society, arranged for the publication of a series of letters from Benjamin Franklin, 1747 to 1750, describing his experiments on electricity. Franklin demonstrated his new theory of positive and negative charges, suggested the electrical nature of lightning, and proposed a tall, grounded rod as a protection against lightning. These experiments established Franklin's reputation as a scientist, and in 1753 he received the Copley Medal of the Royal Society for his contributions to the knowledge of lightning and electricity.
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Benjamin Franklin's formulation of a general theory of electrical “action” won him an international reputation in pure science in his own day. Writing to Dutch physician and scientist Jan Ingenhousz, Franklin responds to a number of his friend's questions about electricity and the Leyden jar, an early form of electrical condenser. In this draft scientific report, it appears that Franklin wrote his answers first using dark ink, leaving room for the questions, which he wrote in red ink.
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In this lengthy essay intended for his fellow scientist Jan Ingenhousz, Benjamin Franklin attempted to explain the effects of lightning on a church steeple in Cremona, Italy, by describing the effects of electricity on various metals. He based his hypothesis on other written accounts, and used this sketch of a tube of tin foil to aid in his explanation.
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Mapping the Gulf Stream
Although Spanish explorers had described the Gulf Stream, Franklin, fascinated by the fact that the sea journey from North America to England was shorter than the return trip, asked his cousin, Nantucket sea captain Timothy Folger, to map its dimensions and course. Franklin published this map and his directions for avoiding it in the Transactions of the American Philosophical Society in 1786. Systematic research, conducted by the U.S. Coast Survey, of the Gulf Stream did not occur until 1845.
Benjamin Franklin. “Maritime Observations and A Chart of the Gulph Stream.” in Transactions of the American Philosophical Society. Philadelphia: 1796. Engraved map. Geography & Map Division, Library of Congress (40A) [gmd9/g9112/g9112g/ct000136]
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Despite his eminence in scientific circles, Benjamin Franklin remained concerned with the more practical applications of scientific study. This sheet entitled “Definition of a Cold” is one of a series bearing Franklin's notes for a paper he intended to write on the subject. Exercise, bathing, and moderation in food and drink consumption were just some of his steps to avoid the common cold.
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Benjamin Franklin's interest in the mystery of the “Northern Lights” is said to have begun on his voyages across the North Atlantic to England. He ascribed the shifting lights to a concentration of electrical charges in the polar regions intensified by the snow and other moisture. He reasoned that this overcharging caused a release of electrical illumination into the air. In this essay, which he wrote in English and French, Franklin analyzed the causes of the Aurora Borealis. It was read at the French Académie des Sciences on April 14, 1779.
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Before leaving London in July 1762, Franklin wrote to the Italian philosopher Giambatista Beccaria. Not having anything new to report on their shared interest in electricity, Franklin described the improvements he had made to the musical glasses invented by Richard Puckeridge. By fitting a series of graduated glass discs on a spindle laid horizontal in a case and revolving the spindle by a foot treadle, Franklin could create bell-like tones by touching his wet fingers to the revolving glasses. Franklin's armonica became popular in Europe, with Mozart and Beethoven composing music for it.
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