Experiments and Observations on Electricity

Background

Franklin was first attracted to the study of electricity when he saw a showman named Archibald Spencer do magic demonstrations in Boston (1743) and in Philadelphia (1744). He purchased Spencer's equipment and used it for his electricity experiments after these lecture demonstrations. He referred to Archibald as Dr. Spence from Scotland. Then, in 1746, at the age of forty years, Franklin began turning over the affairs of his printing company to his business partner David Hall, and went into semi-retirement so he could carry out research on electricity using initially Spencer's equipment.

Peter Collinson – a wealthy Quaker cloth merchant, a Fellow of the Royal Society and one of the founders of the Society of Antiquaries of London – donated (in 1746) a Leyden jar battery, a glass tube, and an account of new German experiments in electricity to the Library Company of Philadelphia (founded by Franklin) on how to make electricity from the glass tube. Franklin first experimented with static electricity in the middle of 1747, referring to it as "these new wonders." In conducting his electrical research, Franklin made use of the unique battery, glass tube, and an electrostatic machine provided by Thomas Penn, son of William Penn—working with a team made up of Ebenezer Kinnersley, Thomas Hopkinson, and Philip Syng. To these he added an electricstatic generating machine of his design that was more efficient than the one given to him. It was convenient because it was constructed with a handle, like that of a common grindstone, thru which a simple mechanical machine mechanism spun an axle that had mounted on it a glass sphere that rubbed on a cloth pad. The glass sphere bulb then generated 'electric fire' (an electric charge) that was transferred through conductors to a Leyden jar capacitor that held the electric charge that was used then for experimentation. Franklin had then formed the first scientific research laboratory in America with this equipment. He used the method of experimentation, and considered his findings to be non-speculative as something anyone could repeat or prove themselves if they wanted to.

Contents

Franklin spent much time studying this new field of electricity, and from 1747 through 1750 sent many letters and papers to Collinson of his findings. These were from his experiment investigations and the observations he made from them. Franklin sent these to Collinson to show that the equipment – put into the hands of the group of men associated with Library Company of Philadelphia – was being put to good use. In these letters, he introduced technical words that we use today for things related to electricity such as plus, minus, positive, negative, charge, discharge, armature, electric shock, electrician, condenser, conductor, and battery.

William Watson, a scientist specializing in the study of electricity, theorized that perhaps electricity was attracted to conductors that were pointed. Watson received in 1746 from Dr. John Mitchell a lengthy Franklin paper on theories about thunderstorms and pointed conductors as related to electricity. He read part of it to fellow members of the Royal Society of London on November 9, 1749. A week later he finished the reading. On December 4 Watson received another similar Franklin paper dated April 29, 1749, from Collinson and read it to the Society on December 21, 1749. Over the next two years Collinson had transmitted to the Society more of Franklin's letters he had received describing electrical experiments done by Franklin and his team of experimenters. Many talked about the tenancy of an electrical discharge to be attracted a pointed conductor that was grounded - the basics to his lightning rod invention to protect wooden buildings such as houses and churches.

Franklin talked about "electrical fire" principles in this first set of letters. One conclusion he wrote Collinson about on June 5, 1747, from these experiments was that it was an element of species of matter in all objects. He came to the conclusion that all objects have an equal balance of element objects. Franklin determined that a friction rubbing process like that of rubbing glass with a cloth does not create these special elements, but only temporary in an instant groups them together and that is collected into a Leyden jar of water and metals. He determined this combination had a tendency to better hold this grouping of "electrical fire" which gave them an abundance or loss of these element objects. He labeled a loss as negative (minus) and a gain as a positive (plus). These losses and gains of electrification were in exact proportions and today is known as the law of conservation of charge. It is an important principle used today to explain modern science of microphysics to the electrification of gross bodies.

Watson turned over some of these Franklin letters to the local publisher Edward Cave, who had them printed in The Gentleman's Magazine in 1750. In 1751 Cave printed in a pamphlet all the letters Collinson received to that point in time. This publication was titled, Experiments and Observations on Electricity, Made in Philadelphia in America by Mr. BENJAMIN FRANKLIN and Communicated in several letters to Mr. P. Collinson of London, F.R.S (London). It was a pamphlet of eighty-six numbered pages. The pamphlet included an unsigned preface written by Dr. John Fothergill. This first publication of Experiments and Observations on Electricity sold for half a crown.

Franklin's first experiments explained in this first set of letters to Collinson was that the Leyden jar, a type of capacitor, had equal and opposite charges on the inner and outer conductors. This was shown in illustrations in his book. The significant Franklin theory introduced to Collinson in a letter dated April 29, 1747, was the concept of the "dissectible condenser." Today we call this distribution of charges in a device, a capacitor. He observed that a charge was built up on both sides between a piece of nonconducting material. In the case of the Leyden jar this was glass (nonconducting matter) and on each side of it was a metal material (conducting matter). These opposite metal layers had the exact opposite electric charges (positive and negative). He observed that with the wire on the inside of the jar was electrised positively a certain amount, that the outer conductor simultaneously became electrised negatively in the same proportion.

Franklin explained in these letters that in an experiment he did it showed that the charge was in the glass itself and not in the water within the jar, as had been theorized by others. After a Leyden jar was charged he poured the water from it into another Leyden jar that was not charged. It turned out the electric force was not condensed in the water itself, as the new Leyden jar had no charge with this water from the first Leyden jar. Then the first jar was refilled with fresh water and it was discovered that there was a charge in this jar. The conclusion then was that it was the glass itself that was condenser of the electric force. It was further determined by more experimentation that it didn't matter what shape the glass was in or if an object was shaped like a glass bottle. It was finally determined that a property of the glass itself was this "force" of equal and opposite charges.

Franklin further explains in these letters that the jar did not electrically balance itself, but a wire of some conducting material had to make contact from the inner conductor (plus) to the outer conductor (minus). This way Franklin observed the balancing and combining of the two different states of electricity in the "miraculous bottle." In the later editions of the book Franklin explained in his letters and showed in illustrations an assembly of Leyden jars that he termed "electrical battery" following the military term idea of an assembly. Franklin assembled a number of parallel-plate condensers consisting of 11 plates of glass and each were "armed" with a lead metal sheet on each side. He hooked them together with wires in a series and then a master wire was attached that could then discharge (balance) the battery when touched to both sides.

Editions

There was a French translation, published in 1752, which contained an experiment suggesting that a long, pointed iron rod would attract a lightning bolt from a thunderstorm cloud. This was prelude to Franklin's lightning rod invention. Frenchman Thomas-Francois d'Alibald did the experiment May 10, 1752, as Franklin had suggested and lightning struck the iron rod. In London it was repeated in Spital square on July 20, 1752, and again in Chelmsford, Essex, on August 12, 1752. The electricity attraction from a lightning storm was also done by Franklin himself in the kite experiment that he talked about in a letter to Collinson dated October 19, 1752. There was even a man by the name G. W. Richman killed in 1753 from electrocution doing his kite experiment. Franklin had proven that lightning bolts and electricity were one and the same. He also showed that this "electric fluid" was attracted to a sharply pointed object high in the sky. An iron rod could have the other end put into the ground to create a path for safe conduction of the high voltage electricity. Thus, a way of diverting lightning bolts from wooden buildings – and preventing them from going aflame due to lightning hits – had been discovered. Franklin's lightning conductor invention, with its lightning rod uppermost point, became a model for the lightning-protection system used in American in the eighteenth century.

The publication for his scientific observations on electricity made Franklin famous throughout Europe as a serious scientist, as Galvani, Volta, Coulomb, and Ampere were. King Louis XV honored Franklin after seeing some of the electrical experiments done in the royal palace at St. Germain near Paris, France. However physicist Jean-Antoine Nollet (1700–1770), a skeptic that had published his own theory on electricity, declared Franklin's ideas were wrong. He claimed in 1753 that Franklin's lightning rod was not only dangerous but useless and would only attract lightning bolts for wooden buildings, causing them to be hit more often. Franklin in time proved to the scientific community that his lightning rod invention not only was a protective device, but it also served as a preventive way to divert destructive lightning bolts away from hitting buildings.

The second English edition (1753) had additional material added to the first English publication of 1751. It went under the title, Supplemental Experiments and Observations on Electricity, Part II made at Philadelphia in America, By Benjamin Franklin, Esq., and communicated in several Letters to P. Collinson, Esq. of London, F.R.S. London: E. Cave, 1753. The second edition was published for distribution also in 1754 and retitled New Experiments and Observations on Electricity, Part III made at Philadelphia in America, By Benjamin Franklin, Esq., and communicated in several Letters to P. Collinson, Esq. of London, F.R.S. London: E. Cave, 1754. It had more pages of letters added. For example, it had additional testimonial letters not written by Franklin added debunking Nollet and coming to Franklin's defense on lightning theory. This edition sold for 2 shillings and 6 pennies in British money. The third edition added another 44 pages of letters that were numbered 111–154. It was published in 1760, 1762, and 1764.

Legacy

There was an expanded fourth edition in 1769 in the form of a book with a front and back hard cover. Franklin added more pages and personally supervised this publication while he was in London. The 1769 book contained additional letters and papers on other science subjects that he had theories on. This edition also had copper plate illustrations of electrical experiments he did. He then supervised and helped publish a fifth edition in 1774 which consisted by then 496 pages. The fifth edition printed in 1774 was similar to that of the 1769 edition and contained additional updated material.That made a total of five English editions during Franklin's lifetime. There were eleven editions of Experiments and observations on electricity. In addition to the five English editions and three French editions, the book had German, Italian and Latin versions. All editions of the book were being printed in Europe until 1941 when the first publications of it were done in the United States. The book is Franklin's only scientific work, and is recognized by some as America's most important scientific publication of the eighteenth century.

Benjamin Franklin was given the Copley Medal by the Royal Society in 1753 in recognition of his work in electricity as reported in this book. He became a Fellow of the Society after his name was submitted the required ten times (one included the Society's president, Lord Macclesfield. Also he was given an honorary degree at the College of William and Mary in 1756 and elected into the French Academy of Science in 1772 because of this book. The theories that Franklin developed in the book formed the basis for subsequent research on electricity.