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Bifocals. A bifocal lens with areas of differing magnification. Bifocals with separate lenses. In this case, the Swedish ethnologist Jan-Öjvind Swahn [ sv]. Bifocals are eyeglasses with two distinct optical powers. Bifocals are commonly prescribed to people with presbyopia who also require a correction for myopia, hyperopia, and/or astigmatism .
Benjamin Franklin FRS FRSA FRSE (January 17, 1706 [ O.S. January 6, 1705] [ Note 1] – April 17, 1790) was an American polymath: a leading writer, scientist, inventor, statesman, diplomat, printer, publisher and political philosopher. [ 1] Among the most influential intellectuals of his time, Franklin was one of the Founding Fathers of the ...
Franklin's electrostatic machine is a high-voltage static electricity - generating device used by Benjamin Franklin in the mid-18th century for research into electrical phenomena. Its key components are a glass globe which turned on an axis via a crank, a cloth pad in contact with the spinning globe, a set of metal needles to conduct away the ...
Benjamin Franklin in the 1780s developed the bifocals. Bifocal lenses advanced little in the first half of the 19th century. The terms bifocal and trifocal were introduced in London by John Isaac Hawkins, whose trifocals were patented in 1827. In 1884 B. M. Hanna was granted patents on two forms of bifocals which become commercially ...
Thirteen Colonies. Observations Concerning the Increase of Mankind, Peopling of Countries, etc. is a short essay written in 1751 by American polymath Benjamin Franklin. [ 1] It was circulated by Franklin in manuscript to his circle of friends, but in 1755 it was published as an addendum in a Boston pamphlet on another subject. [ 2]
71000062 [1] Added to NRHP. June 24, 1971. Christ Church Burial Ground in Philadelphia is an important early-American cemetery. It is the final resting place of Benjamin Franklin and his wife, Deborah. Four other signers of the Declaration of Independence are buried here, Benjamin Rush, Francis Hopkinson, Joseph Hewes, and George Ross.