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Building Science

The Mad Hatter, Isaac Newton, and That Old Thermostat

Ruminations on life, mercury, and the environment

Image 1 of 4
The Mad Hatter, although modeled after a furniture dealer in Lewis Carroll's book, got his name from the expression 'mad as a hatter.' The origins of the phrase are unclear, but the behavior of hatters wasn't. Because of exposure to mercury, they had neurological problems that made them a bit odd.
Image Credit: Wikimedia Commons
The Mad Hatter, although modeled after a furniture dealer in Lewis Carroll's book, got his name from the expression 'mad as a hatter.' The origins of the phrase are unclear, but the behavior of hatters wasn't. Because of exposure to mercury, they had neurological problems that made them a bit odd.
Image Credit: Wikimedia Commons
This 1941 Honeywell thermostat operates mechanically and is unaffected by cosmic rays. This one is still in use in the Minneapolis area.
Image Credit: Guy Theriot
This thermostat also operates mechanically, using bimetallic strips that expand and contract with temperature. When they do change size, the vials filled with mercury tip one way or the other and open or close the circuit.
Image Credit: Energy Vanguard
A closeup of two of the mercury vials in that old thermostat.
Image Credit: Energy Vanguard

I was a kid a long, long time ago. Seems like it was another century … another millennium even. Wait a minute — it was another millennium!

That was back in the day when we used to ride bicycles without helmets, apply mercury to our wounds, move seat belts out of the way (if the car even had them), and put our tongue on steel poles in the middle of winter. Of course, in Texas and Louisiana we just ended up with a bad taste in our mouth from those steel poles and wondered why people made such a big deal about it.

It was so long ago that our grandparents had stuff in their houses that you’ve probably never even heard of. I loved going to Mammaw and Pappaw’s house because they had all kinds of cool, old stuff. Even better, Pappaw had a warehouse full of even older, old stuff and a shop for his business (Bailes Electric Co.) that had the most enticing stuff ever.

Playing with old equipment

For example, he had voltmeter probes hanging down right next to an electrical outlet. Of course, I had to stick them in there. I don’t know how it happened, but my recollection is that I made sparks … and got in trouble.

And then there was that fascinating lamp way up on the top shelf. It had a blue bulb, so I just had to plug it in and see how beautiful the light was. Got sparks that time, too. Old stuff is really cool!

Take that old thermostat you see below. It’s from 1941. Back then, nobody had any of this newfangled digital stuff with thermistors and integrated circuits. No, it was mechanical, and it worked. Random cosmic rays zipping through the device never threw things off, forcing you to reboot the system. If it didn’t work, you could take the cover off, find out what was wrong, and fix it.

Now, if some piece of digital equipment doesn’t work, a technician hooks up a computer to the device’s computer then tells you they have to replace the innards — or the whole thing. There’s not much fixin’ anymore.

My friend Guy Theriot posted the photo of that old thermostat on Facebook recently. Guy and I go way back. Although he lives in Minnesota now, he’s a Cajun. He was a friend of mine down the bayou in Chauvin, Louisiana, and we hung out together a lot in my first few years with the Cajuns.

About those old thermostats…

The old thermostats, as I said above, operated on mechanical principles. In the thermostat shown below, a bimetallic strip expanded or contracted with temperature because of the different thermal expansion coefficients of the two metals. That strip was connected to vials of mercury. The vials tilted as the bimetallic stip changed size, and the mercury would either complete the circuit or cause the circuit to be open. The thermostat below has two bimetallic strips and four vials of mercury — two separate mechanisms for heating and cooling.

When the mercury went one way in the vial, electricity flowed and the heating or cooling system came on. When it went the other way, the electricity didn’t flow and the HVAC system was off. Simple and elegant! That’s how we rolled back then.

The downside of that simplicity and elegance was rivers on fire, smog that burned your eyes, and kids who weren’t wearing seatbelts getting thrown out of cars. Buddy Meyer was a friend of mine and Guy’s. The last time I saw him was the summer of ’73, right before my dad took me and my sisters to Leesville for two months. I remember Buddy, Guy, and I were riding our bicycles one day. Two months later, I arrived back in Chauvin and heard from my mom that Buddy was dead, thrown from his uncle’s truck when they crashed. We didn’t wear seat belts then.

Mad as a hatter

Back to those old thermostats now: the mercury they contain is a toxic material. When I was a kid back in the last millenium, we’d put it on our scraped knees. It was red and it stung like the dickens. (I’ve never been stung by a dickens, or even seen one, but I imagine it as a wasp about the size of a coyote with fierce looking, bloodshot eyes and a huge, poisonous stinger.) It came in little brown bottles with a screw top that had a built-in eyedropper. Mammaw called it mercurochrome. Now it’s banned by the FDA.

Mercury, as it turns out, is pretty darn toxic. Dartmouth chemistry professor Karen Wetterhahn found out the hard way. She was working with dimethylmercury, one of the most toxic mercury compounds, and accidentally got some on her gloves. It went through, got into her blood, and she was dead in a year.

Isaac Newton, known to have had a nasty dispostion and a bit of paranoia at one point in his life, is also believed to have suffered from mercury poisoning. Around the time he was doing experiments with mercury, he “accused friends of plotting against him, slept little, and reported conversations that did not exist.”

And then there was Alice’s friend, the Mad Hatter. He wasn’t the only hatter who had mental challenges. Evidently it was common because of the mercury they used when felting the hats they made. The expression ‘mad as a hatter‘ may have its origin in mercury poisoning.

Mercury and energy

Old thermostats aren’t the only place you find mercury in the world of energy production and consumption. It’s also in fluorescent lights, both the straight tube and the compact fluorescent lamp (CFL) forms. Both should be disposed of properly. Compared to thermostats, though, they contain a tiny amount of mercury.

The largest single source of mercury is burning coal to produce electricity. “Coal-burning power plants are the largest human-caused source of mercury emissions to the air in the United States, accounting for over 50 percent of all domestic human-caused mercury emissions,” according to the US EPA.

The moral of the story is that when old timers like me say that we were so much tougher back in the day, be sure to keep it all in perspective. Yeah, some things were better, but in other respects, we’re better off now. Mercury’s not something to mess around with. If you’ve got an old thermostat or dead fluorescent lamps, don’t just throw them in the trash.

Allison Bailes of Decatur, Georgia, is a speaker, writer, energy consultant, RESNET-certified trainer, and the author of the Energy Vanguard Blog. You can follow him on Twitter at @EnergyVanguard.


  1. dankolbert | | #1

    Well put
    Toxic chemicals have certainly made many of our lives a lot easier, but now we're drowning in it and it's time to pay the piper. I'm on my way to the dump right now, and fortunately they accept fluorescent bulbs and old t-stats for recycling - I've got one with me now.

  2. user-1087436 | | #2

    Oh yeah.
    I remember mercurochrome, and merthiolate, and the bottle with the little glass wand that stung like hell when you daubed it on the wound. And then there was the tiny bottle of pure liquid mercury that I somehow acquired as a kid. I played with it, stuck my finger in it, watched the little globules split up and reform. I feel now as if I played with dynamite and didn't know it. I wrote a book once about a 19th century doctor who poisoned himself with his own medicine, in this case calomel or mercurous chloride. An emetic and general all-purpose curative, it was a substance no doctor would have been without.

  3. GBA Editor
    Martin Holladay | | #3

    Me too
    I also had a little glass bottle of mercury that I loved to play with. I used to pour it in my palm and watch it move around before returning it to its little bottle.

  4. GBA Editor
    Allison A. Bailes III, PhD | | #4

    Mercury mayonnaise
    I don't recall playing with mercury as a kid, although I may well have, but I do remember that we had a mayonnaise jar full of it in the lab I worked in when I was in grad school. It had been there for decades in a cabinet with a bunch of other relics. It was quite heavy, mercury being more than 13 times as dense as water, and it would have been quite a mess had anyone dropped that jar. I think we got rid of it while I was there.

  5. jinmtvt | | #5

    Family business is a car
    Family business is a car recycling yard ...
    we are currently ( have been for 4-5 years i believe ) mercury filled "hood light switches "
    from some USA cars ( can't believe they are still using this system in 2002-2003 ... mainly GM )
    We send them for recycling its content at a government assigned lab ( good thing )

    I am not really old ( getting to 34 this year ! ), but i do recall using "mercurochrome " when i was young on the 2000000000s wounds i had . My mom still has an old bottle at her place that she just doesn't want to get rid of ( i'll try and snip it while she ain't there soon ..for disposal )

    About old time stuff ...they only thing i hate about recent products is how hard and expensive it is to find a product that was actually designed to last more than 1-2 years ( or actually a product that was engineered ...most aren't )

    Man did old stuff seem to last forever even if not efficient ...
    we are still running an 1960-70 Devilbiss 4 pistons ( 2 heads ) air compressor 8hours /day , 5-6 days week it has been doing so all that time , working hard all the time,
    with only a recent oil ring replacement and no other maintenance ( we might have changed oil once i believe )

    Ahaha , and to think of it , a few years back ( maybe 6-8 ) i was looking at building a ~1.5m telescope using the "rotary-mercury filled " design super smart ...
    Would've been a delight to use around kids!! ( neway it can only point straight up so it is a bit boring and time restrictive )

    ok enoughbblabla ..

  6. user-1127834 | | #6

    I don't see it evaporatin !
    Just had to believe Dad. his interest in Chem as a Miami U BS and 2 years art acadamy and mixed paints too.

    Told me one day as I began to collect the stuff on th floor from breaking the thermometer, "get away, it evaporates like water sorta..." and he made me leave it there for him to clear up.

    Thanks Dad! ( he had 5 yr Marine Corps to '45 as Camof and Demolition works with explosives on the Islands...and made his own clay from OH that is still fresh today from the 50's, that has alittle silly putty and bees wax in it... taught me electricity at 10yrs... and wiring and rewiring slot car motors in 1967 at his raceway and maintained 3 years his hand made beautiful lacquered 135 ft 24th scale track, wet sanded and copper taped (not brade)...thanks Dad!)...

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