A man of many talents, Benjamin Franklin was not one to back down from a challenge – even if that challenge was defying age. As he grew older, Franklin’s vision, which had never exactly been amazing, began to deteriorate to the point where his glasses no longer helped. Needing, now, to carry around two pairs of glasses, Franklin quickly became annoyed and set his mind to solving the problem. The result… Benjamin Franklin invented the bifocals. 

Benjamin Franklin the Scientist

The bifocals, or double spectacles as he called them, weren’t Franklin’s first foray into optics. For decades, Franklin had been interested in telescopes. Having made a name for himself as one of America’s more scientific thinkers, Franklin opened correspondence with leading opticians in the colonies and England.

For the better part of three decades Franklin played the role of middleman between opticians on either side of the Atlantic. As several of letters show, Franklin helped communicate the advances each of these men made with each other. Whether it was the shape or materials used in making lenses, or the hardware needed to make telescopes more useful, Franklin was all up in it.

In January, 1764, James Bowdoin, a leading astronomer, wrote to Franklin from Boston for his help improving a telescope. In this correspondence, Bowdoin asked Franklin to send his latest ideas on telescopes to John Canton, a leading English physicist of the day.

“I here enclose, open for your perusal, a Letter to Mr. Canton on the Subject I spoke to you about, Bowdoin wrote. “If any thing should occur to you to improve the Telescope further than what is noticed in said Letter, I shall take it as a favor you would mention it to Mr. Canton; and that you’d be so good as to let my letter accompany your own.”1

Along with the letter, Bowdoin included an image of the telescope he wanted Franklin’s help in improving:

An illustration of a telescope drawn by a friend of Benjamin Franklin.

But, from Bowdoin’s letter, we can also see Franklin did more than connect scientists in America and Europe – he can also be seen as a founding member of the science optics. Why else would have Bowdoin tell Franklin that “if any thing should occur to you to improve the Telescope further…I shall take it as a favor you would mention it to Mr. Canton…”?

How Benjamin Franklin Invented the Bifocals

Whether it was the years stooped over parchment, reading by candlelight, or simply the vicissitude of aging, Franklin actually developed both presbyopia and myopia. Or, for those who aren’t doctors or fluent in Latin, he was both nearsighted and farsighted. 

Unfortunately for Franklin, he lived in a time before you could just enlarge the text on your device to make it easier to read. So, avid reader that he was, Franklin developed the habit of carrying around two pairs of glasses at all times. As you can imagine, this quickly became annoying.2

But, rather than live in a perpetual state of annoyance, Franklin put his years of correspondence with opticians to good use.

“I… had formerly two Pair of Spectacles, which I shifted occasionally, as in travelling I sometimes read and often wanted to regard the Prospects,” Franklin recalled in a letter to his friend Georege Whatley. “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.”3

Franklin included the below illustration in this letter to Whatley, which detailed how exactly how constructed his bifocals by splitting each lens in half.

An illustration of Benjamin Franklin's design for bifocal glasses.

Franklin hoped his bifocals would prove useful for others, too. ” I imagine it will be found pretty generally true, that 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,” he told Whatley.4

Out of this sense of helping the general public see objects near and far, Franklin never took out a patent on his bifocals.

Why Benjamin Franklin Invented the Bifocals

As we’ve already noted, Benjamin Franklin loved himself some books. He had, afterall, spent nearly half his life making a living as a printer. But, as his vision began to trouble him, the printed word that he loved so much started to blur. “I cannot distinguish a letter even of large Print…” Franklin once wrote to Whatley in 1784.5

At the same time that Franklin began developing the idea for his “double spectacles,” he was also served as an American diplomat in France. While he gained enough fluency in French to get by, Franklin himself readily admitted he was no master at the language. And hw could he be? He’d spent his entire life in Boston and Philadelphia, not exactly ideal places to immerse oneself in the French language. 

Painting of Benjamin Franklin meeting the French nobility in Paris.
Franklin meeting the women of Paris, no doubt staring at their faces to try and better understand the French language.

As such, Franklin found that watching the faces of the people he spoke with helped him discern the foreign words rolling off their tongues. “… when one’ Ears are not well accustomed to the Sounds of a Language, a Sight of the Movements in the Features of him that speaks helps to explain, so that I understand French better by the help of my Spectacles,” Franklin wrote to Whatley from his home in Passy, France in May of 1785.6

Turns out, we may have France to thank for the final feather in the cap of America’s first great inventor.

Sources for Benjamin Franklin and his “Double Spectacles”

  1. “To Benjamin Franklin From James Bowdoin, 18 January 1784,” founders.archives.gov
  2. “Bifocals and More: Focus on Ben Franklin,” infocus.nlm.nih.gov
  3. “To George Whatley, Passy, May 23. 1785,” franklinpapers.org
  4. Ibid
  5. “To George Whatley, Passy, near Paris, Augt. 21. 1784,” franklinpapers.org
  6. “To George Whatley, Passy, May 23. 1785,” franklinpapers.org
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