FRANKLIN, Benjamin (1706-1790). Experiments and Observations on Electricity, Made at Philadelphia in America To Which Are Added, Letters and Papers on Philosophical Subjects. Fifth Edition. London: F. Newbery, 1774.
4o (251 x 195mm). Half-title, seven engraved plates (two folding) by J. Hulett and B. Cole, six text woodcuts, several examples of printed music. (Small paper flaw in margin of M4, clean marginal tears neatly mended at AA3, CC2, GG1, final blank Yyy2 excised, small ink mark in margin Xxx2v of Index.) Contemporary blue-gray paper boards, ENTIRELY UNCUT (spine renewed in period style, boards rubbed, corners worn); quarter morocco folding case.
Fifth Edition. PRESENTATION COPY OF FRANKLIN'S MOST IMPORTANT SCIENTIFIC PUBLICATION, boldly inscribed in ink by Franklin at top corner of preliminary blank: "For Mr. Bentley from The Author." The work is written in the form of a series of letters addressed to a variety of correspondents in London and America, notably Peter Collinson, Colden, Beccaria and others, some of which had been delivered at the Royal Society. The electrical experiments include Franklin's famous experiments of the late 1740s using the Leiden jar, which resulted in a successful analysis of electrical properties and the proposition of the "single fluid" theory of electricity to explain induced charges. Also included in this section are the well-known experiments with kites carrying a conductor (a key): "the most dramatic result of Franklin's researches was the proof that lightning is really an electrical phenomenon. Others had made such a suggestion before him--even Newton himself--but it was he who provided the experimental proof. In 1752 he flew a kite in a thunderstorm and attached a key to its string. From this he collected electric charges in a Leiden jar and showed that atmospheric and frictional or machine-made electricity are the same. "Experiments and Observations remains the most important scientific book of eighteenth-century America" (PMM). The sizeable portion of the book which comprises the "Letters and Papers of Philosophical Subjects" (pp.190-514) contains a remarkably wide-ranging series of letters and experiments such as "An Account of the new-invented Pennsylvanian Fire-Places" (the Franklin stove, with plate), the effects of lightning and the design of lightning rods, magnetism, St. Elmo's fire, the source of the common cold, electrical effects of amber, the teaching of swimming, the nature of tides, waterspouts and hurricanes, the rapid increase in population in the American colonies, speculations on the advantages and disadvantages of the colonies uniting under a single government (p.347), "Scotch tunes, the pleasure they give explain'd," small-pox and its spread, the experiments on the relative reflectivity of different color cloths, and "Hats, ladies' summer, of what colour best."
Richard Bentley the younger (1708-1782) is likely to have been the acquaintance to whom Franklin inscribed this copy. A minor playwright and occasional author, Bentley may have had scientific or pseudo-scientific interests; he published an account of an Earthquake in 1750, a curious tract on a supposed centaur, and epistles to various persons, including Charles James Fox (CBEL II, 459). A FINE COPY. First edition: Dibner Heralds 57; Grolier/Horblit 31a; Norman 830; PMM 199; Sabin 25506.