Today in History: Benjamin Franklin describes his invention of bifocal glasses
American statesman Benjmain Franklin addressed a letter to George Whatley in 1785, describing a pair of bifocal glasses.
On 23 May 1785, Benjamin Franklin addressed a letter to his friend, George Whatley, in which he described how he had possibly invented bifocal glasses, and what purpose they could serve. Franklin himself wore glasses continually after 1776, admitting in 1784 that without them he could not ‘distinguish a letter even of large print’.
In 1779, Franklin ordered a pair of glasses from an English optician, Sykes.
Sykes later wrote to Franklin explaining that his spectacles had been delayed due to the lenses having broken three times during cutting. This has been taken as evidence that he was ordering something out of the ordinary.
In a letter written to Whatley in August 1784, Franklin declared himself “happy in the invention of double spectacles, which serving for distant objects as well as near ones, make my eyes as useful to me as ever they were.”
These glasses were described in more detail in the letter from Franklin to Whatley referred to above. In this letter, he again referred to ‘my double spectacles’ (where ‘my’ need only signify ownership) and provided a sketch of the spectacles.
The letter continued: “The same convexity of glass, through which a man sees clearest and best at the distance proper for reading, is not the best for greater distances. I therefore had formerly two pair of spectacles, which I shifted occasionally, as in travelling I sometimes read, and often wanted to regard the prospects. Finding this change troublesome, and not always sufficiently ready, I had the glasses cut and half of each kind associated in the same circle. By this means, as I wear my spectacles constantly, I have only to move my eyes up or down, as I want to see distinctly far or near, the proper glasses being always ready”.
Some historians have, however, suggested that in this letter to Whatley, Franklin refers to an experiment carried out more than 20 years earlier in London.
A letter from newspaper editor, John Fenno, to his wife dated 8 March 1789, supports this theory.
In it, Fenno describes a meeting with Franklin in which the elderly statesman had mentioned wearing spectacles for many years: “He informed me that he had worn spectacles for 50 years; each eye appeared to be formed of two pieces of glass divided horizontally – he informed me that he had always worn such.”
The Fenno letter also fits in with the fact that Franklin suffered from hyperopia (farsightedness), requiring spectacles for this condition as early as the 1730s. This would have made him likely to have benefited from bifocals by the time he arrived in London in 1757.
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