Did Benjamin Franklin Invent the Bifocal?
Historical documents, including writings by Franklin and his contemporaries, show that he was one of the first to be documented as using and wearing bifocals. Franklin definitively mentions the split-lens spectacle in 1785; a letter written by a friend in 1789 claims that he had used them for the past 50 years. However, no one patented the bifocal until 1836.
Evidence suggests that other people may have also invented their own version of the bifocal at around the same time. Some think that Franklin, given his prominence in history, could be unduly credited with the invention.
A video about Franklin’s top 5 inventions including the bifocal.
Did Others Invent Bifocals Before Franklin?
The idea of a split-lens had been suggested by Zahn in 1683 and, by Hertel in 1716. This was well before Franklin was thought to have invented them in the mid to late 1770s. However, there is no indication that the Zahn and Hertel lenses served the same purpose as the modern Bifocal.
Between 1760 – 1800 Franklin, his friend Benjamin West, and several people in their “circle” are thought to have potentially invented or have been early adopters of the new technology. It is possible that the concept of split-lenses was passed around during this time with many different “inventors” ordering optometrists to make versions of the bifocal. It is possible that the idea originated with Franklin, but there is no hard evidence showing that this is the case.
The Evidence We Do Have
The following evidence is usually used when discussing the invention of the bifocal:
- We know split-lens were mentioned by Zahn in 1683 and, by Hertel in 1716 although they may not have served the same purpose as the bifocal.
- An oil painting by royal academician Stephen Elmer, dated 1777, of Franklin, shows Franklin wearing what could be bifocals.
- While on a diplomatic mission to France in 1779 Franklin ordered a costly (18F) pair of custom spectacles from the English optician, Sykes, who had a business on the Place du Palais-Royale. The lenses were delayed as they broke 3 times during the cutting process. It’s very likely he was ordering bifocals.
- In 1784, Franklin said that without spectacles he could not “distinguish a letter even of large print.”
- In a letter of August 1784, written to his friend George Whatley, Franklin said he was “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.” However, he never claims to have invented this double spectacle in the letter.
- In another letter to Whatley, dated 23 May 1785, Franklin refers to the spectacles as “my double spectacles.” Despite the phrasing, the rest of the letter doesn’t claim the invention of the bifocals, only the use of them.
- The rest of the May 23rd letter reads: “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 traveling 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.”
- A letter from the newspaper editor, John Fenno, to his wife dated 8 March 1789 describes a meeting with Franklin:”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.”
If Franklin Invented the Bifocal Why Didn’t He Talk About Them More or Patent Them?
We can be confident that Franklin was aware of the bifocal by 1784 and was wearing them (presumably for years), but it is rather odd that he did not write more about or try to patent the bifocal if he had actually felt he invented it.
Perhaps he simply did not think the idea would catch on, but again for a man like Franklin, this seems odd. Certainly Franklin seemed to hold the bifocal in high regard given the problems he had with his eyesight, and it is curious to think that he would not have written more extensively about it had he felt he truly invented the split-lens spectacles.