What caused the Mad Hatter to go mad?
Dear Straight Dope:
What caused the Mad Hatter to go mad? Did he sniff the glue in the hat? Was it mercury poisoning? --Jeff Imparato
Dear Straight Dope:
In a discussion of the recent Nicor debacle, the effects of mercury came up, namely that overexposure causes insanity. "In fact," I said, "that's the origin of the phrase 'mad as a hatter,' since people who made hats were exposed to mercury in the course of their work, and it was thus common for aging hatters to go mad." Someone else disagreed, saying that it was the people who wore the hats who were the "mad hatters," because of exposure to mercury residue on the hats. Can you straighten out this disagreement for us?
The most famous Mad Hatter, of course, is the one from the Mad Tea Party in Alice in Wonderland, the partner of the March Hare. Both mad, of course. But Lewis Carroll did not invent the phrase, although he did create the character. The phrases "mad as a hatter" and "mad as a March hare" were common at the time Lewis Carroll wrote (1865 was the first publication date of Alice). The phrase had been in common use in 1837, almost 30 years earlier. Carroll frequently used common expressions, songs, nursery rhymes, etc., as the basis for characters in his stories.
The origin of the phrase, it's believed, is that hatters really did go mad. The chemicals used in hat-making included mercurious nitrate, used in curing felt. Prolonged exposure to the mercury vapors caused mercury poisoning. Victims developed severe and uncontrollable muscular tremors and twitching limbs, called "hatter's shakes"; other symptoms included distorted vision and confused speech. Advanced cases developed hallucinations and other psychotic symptoms.
'Twas the hatters, not the wearers of hats. The hatters were exposed to the mercury fumes, which would have been long dissipated (or of insignificant strength) by the time the hat was worn. This use of mercury is now subject to severe legal restrictions (if not banned) in the U.S. and Europe.
While this is the most widely accepted origin of the phrase, there are those who believe that the phrase was originally "mad as an adder" (meaning poisonous as the snake) which degenerated to hatter. Sounds pretty flimsy to me, but then etymology is not an empirical science.
OK, having answered the question, I can't help but add some trivia.
There have been many guesses about whether Carroll was satirizing any particular individual with his Mad Hatter, or whether Tenniel (the first and most famous illustrator of Alice) was caricaturing anyone. Speculation ranges from Theophilus Carter, a furniture dealer near Oxford (most likely) to Prime Minister Gladstone (highly implausible).
Dropping the H, "Mad Adder" could imply a mathematician, such as Carroll himself. But then we start to move into realms of, well, madness.
As long as we're off the subject, the expression "mad as a March hare" refers to the frenzied capers of the male hare during March, its mating season. Evan Morris of The Word Detective says, "Of course, the hare's behavior probably only appears strange to us--we can only guess how our human courtship rituals might appear to a rabbit. In any case, March Hares can't be entirely bonkers because, after all, every summer brings a new crop of baby hares."
Martin Gardner, author of the wonderful Annotated Alice, reports that two British scientists (Anthony Holley and Paul Greenwood, in Nature, June 7, 1984) made extensive observations of the behaviors of hares in the spring, and found no evidence that male hares go into a frenzy during the March rutting season. They concluded that the main courtship behavior of male hares during the entire breeding period (many months) is chasing females and then boxing with them. Behavior in March is no different from any other month.
Of course, this would not be the first time that popular beliefs and scientific observation don't jibe, nor where popular beliefs have lead to common expressions that are not scientifically verifiable.
Apparently Erasmus (1466?-1536), the Dutch Renaissance scholar and theologian, wrote the expression "mad as marsh hare," and there is now some speculation that this got corrupted to "March" in later decades. However, long before Carroll was writing, the expression was "mad as a March Hare," regardless of scientific validity.
Also worth noting that the Tenniel illustrations of the March Hare show wisps of straw in his hair. It was a Victorian symbol, both in art and on the stage, of madness.
The Hatter and the Hare reappear in Alice Through the Looking Glass as the King's messengers, Hatta and Haigha.
"In that direction," the Cat said, waving its right paw round, "lives a Hatter: and in that direction," waving the other paw, "lives a March Hare. Visit either you like: they're both mad."
"But I don't want to go among mad people," Alice remarked.
"Oh, you ca'n't help that," said the Cat: "we're all mad here. I'm mad. You're mad."
"How do you know I'm mad?" said Alice.
"You must be, said the Cat, "or you wouldn't have come here."