When it comes to historical research, I am a bit of a completionist. There are different styles of doing history, and mine is to be exhaustive. The thing is, with historical research, there are so many sources out there, likely in so many different archives, that for any one project it’s nearly impossible to fully research anything. You just get to a point where you can say “good enough.”

Here’s one story of how I got obsessed with finding out all there was to know, and eventually came to the realization that (unless I have some time and funds to devote to a couple of transatlantic flights) I’ll have to call it good enough. Along the way I’m also going to pull back the curtain a bit on what it’s like to do armchair historical research. It’s not very glamorous, and, once I get into it, it may seem obvious, but this was my process for research here.

It all started with the group photograph above which I wanted to include in the January 2023 Photos of the Month blog post . (The blog post spotlighted photos that included something about tea. Note the tea cups interspersed with the beakers on the table.)

Right away I was in love with this photograph – the half smiles on some people’s faces, the fact that Einstein looks like he just ducked in to photobomb the gathering, and the three (three!) women in it. But, I was also bothered because the identification key was missing information.

The original description as it was on the ESVA website (it has since been updated) was:

For ease of reference, here’s an identification key that I’ll be referring back to throughout the blog post with the identifications as they originally stood:

1. Karl F. Herzfeld
2. Otto Stern
3. Albert Einstein
4. E. Piccard (Weiss’ assistant, later a balloonist)
5. Fortrat (Weiss Assistant, author of Fortrat diagram (frequency of diatomic molecules as function of rot, qu. Number)
6. Miss Grigorjeff, translator of Chevolson’s Lehrbuch der Physik from Russian into German, visitor
   
7. [Along with 9] the two ladies are Dutch high school teachers (van Leeuwen )
8. Paul Ehrenfest
9. [Along with 7] the two ladies are Dutch high school teachers (van Leeuwen )
10. Foex (magnetism)
11. Wolfers

Immediately upon seeing the original key I had questions, largely centering around people’s first names! It’s a frustrating but super common phenomenon with historical photographs that the original captioner will just label the photo with a partial name that seems obvious to them but will inevitably not be to future generations. Probably most of us do this with our family scrapbooks. Of course I know who “Top” and “Bobby” are, but unless you’re one of my relatives reading this blog post (hello!) you would be hard pressed to guess that Bobby is my great grandmother Roberta and “Top” is actually a nickname for a multiple-generations-removed uncle named Effingham, which only makes sense if you happen to know the family story behind it.

#0. “P. Weiss”

So because I’m a completionist, I set out to fill in the missing information in the caption – beginning with who “P. Weiss” was. This turned out to be fairly easy to find out with a quick Google search along the lines of “Weiss Zurich physics.” Pierre Weiss (1865-1940), a groundbreaking figure in magnetism, immediately popped up. After a cross reference to confirm that he had worked at ETH Zurich around 1913 and had even worked with some of the already-identified people in the photograph, I was fairly certain I had found the correct Pierre Weiss (not that there were likely many physicists named Pierre Weiss running around Switzerland at that time).

#4 E. Piccard and #10 Foex

Knowing the context of whose laboratory group is pictured unlocked a lot more names fairly quickly, especially those who had worked for Weiss as assistants. “E. Piccard” was almost certainly a mistaken reference to Auguste Piccard, who worked for Weiss and indeed did become a balloonist as the original caption noted. (He’s even mentioned in Weiss’s Wikipedia page.) Similarly “Foex” was a misspelling of “Gabriel Foëx,” who had worked with Weiss, and even published with him on magnetism which the original caption had helpfully hinted at. Again, Foëx was also mentioned on Weiss’s Wikipedia page, so the most time-consuming part was simply confirming that the details lined up properly, and a Physics Today obituary confirmed the identity clearly.

#5 Fortrat

“Fortrat” took a little longer to pin down, as did Wolfers. I thought Fortrat would be easy - he has a whole diagram named after him! But, at least as of at the time of this writing, most of the information pages online about Fortrat diagrams attribute the diagrams to “Fortrat.” And only Fortrat. No first name. I did quickly confirm with my mother (who coincidentally is a physicist!) that a Fortrat diagram shows the rotational finestructure in a vibrational spectrum, so the original caption that states it shows the “frequency of diatomic molecules as function of rot, qu. [rotational quantum] Number,” I felt could stand.

So rather than investigate through the naming of the diagram, I went back to looking for a Fortrat who had worked with Pierre Weiss. A Google search - for “pierre weiss ‘fortrat’” – revealed that Pierre Weiss had published multiple papers with an “R. Fortrat.” And eventually further digging into publications revealed those by or about a René Fortrat such as this 1929 book review in Nature . Jean-Marc Ginoux’s book History of Nonlinear Oscillations Theory in France (1880-1940), with its multiple citations of Fortrat’s works that I could easily see in just the preview on Google Books, was a helpful confirmation.

#11 Wolfers

For Wolfers I again began with a search for ‘Pierre Weiss “Wolfers”’ too, in the hope that publications between the two would yield an immediate answer. Sometimes if I’m on this search path I’ll dip into Google Scholar and see if I get lucky. Google Scholar isn’t always very complete when it comes to older publications, but sometimes it works. Alas, very often scientists in the early 1900s published with just a first initial. Wolfers seems to have been a not-very-uncommon name, although around the 1910s and 1920s there were many physics articles published by an “F Wolfers.” Going back to a general Google search, looking for “F Wolfers” pulled up way too much noise in the results, but searching for “F Wolfers physics” landed me with success when the first hit was an Arxiv paper by historian Helge Kragh about the naming of the photon. Kragh wrote, “Very little is known of the French physicist Frithiof Wolfers, who apparently changed his first name to Fred and signed his many papers as just “F. Wolfers.” Bingo!

At this point let me update the identification key to summarize where the investigation stood.

1. Karl F. Herzfeld
2. Otto Stern
3. Albert Einstein
4. Auguste Piccard (Pierre Weiss’s assistant, later a balloonist)
5. René Fortrat (assistant to Pierre Weiss, author of Fortrat diagram - frequency of diatomic molecules as function of rotational quantum number)
6. To be determined
   
7. To be determined
8. Paul Ehrenfest
9. To be determined
10. Gabriel Foëx
11. Frithiof (Fred) Wolfers

#6 Miss Grigorjeff

Next I turned to identifying the women in the picture. I thought this might prove to be the hardest of the tasks, and it was so. I began with, as the original caption read, “Miss Grigorjeff, translator of Chevolson’s Lehrbuch der Physik from Russian into German, visitor.” An initial googling of “Grigorjeff Weiss” was far too optimistic and turned up nothing. The way to discover Grigorjeff was almost certainly through the clue that she was the translator of what must have been a relatively well-known book.

Orest Danilovich Chwolson, also sometimes spelled Khvolson as well as Chevolson, was a Russian physicist who worked on gravitational lensing and wrote multiple volumes and editions of his Lehrbuch der Physik in the first decades of the twentieth century. The first edition appeared in 1902. Happily, as is often the case with historical research of topics from over a hundred years ago, various editions of the book were out of copyright. Thus I could look up the book in full on Hathi Trust , check the acknowledgement section, and see if there was more information on Grigorjeff. (Variations are also available to read on Google Books .)

I first knew something wasn’t quite right when I looked at the title pages and noticed that Grigorjeff was not credited with the translation. And indeed looking at the acknowledgements, her role with the book was not at all that of a translator. Chwolson wrote (forgive the poor German translation):

Well, this wasn’t at least too different from the caption. And a misremembering of someone’s role on a project wasn’t that big a mistake. In contrast, I was starting to suspect that Herzfeld (or whoever was the original captioner for the ESVA photograph) had just pulled “van Leeuwen” as a generic Dutch name out of thin air because they couldn’t remember the names of the other two women.

#7 and #9 “The two ladies are Dutch high school teachers (van Leeuwen )”

Fortunately, in the course of earlier searches I had discovered another copy of the same photograph held by ETH Zurich . It was being displayed as part of an online web exhibit on Einstein’s years in Zurich and contained many details about Einstein’s life at the time the photo was taken. Of course, I was most interested in the identification key. Their key corroborated many of my earlier identifications (including Grigorjeff, although their key has it as “Girgorjeff”), but it also offered alternate identifications for the two Dutch women in the photograph. Two women in the top row are labeled as, from left to right, Fraulein Frankamp and Fraulein Bruins.

Their last names were enough to pull up in a quick Google search of “Weiss Frankamp” and “Weiss Bruins” that both had published with Pierre Weiss, and moreover the search revealed through a bibliography in The Scientific Correspondence of H. A. Lorentz that their full names were Catherine A. Frankamp and Eva Dina Bruins.

I reached out to the university archives at ETH Zurich to see if they had any additional information on the photograph, or on Frankamp, Bruins, and Grigorjeff. I heard back from Johannes Wahl, an archivist at the library, who said:

The date range fit for Eva Bruins and Catherine Frankcamp, and they were Dutch women which fit with Herzfeld’s identification. But Grigorjeff (or “Grigorieff”) was a bit more of a perplexing question. According to Chwolson’s book, her initials were “A. J.” not “M” for Marie, although Grigorjeff could have had multiple names and gone by some in certain contexts – and “A” could even be some version of “Annamarie” for all I knew. The fact that she could be confirmed to be in Zurich in 1907/1908 at least hinted that maybe she might have desired to return to visit her former professors, although it wasn’t as good as a confirmation that she was actually in Zurich at the time the photograph was taken.

I decided to put Grigorjeff aside for the moment and concentrate on the two Dutch women. As a reminder, these are numbers 7 and 9 in the photograph. To begin, Eva Bruins was a doctoral student of Hendrik Lorentz at the University of Leiden. In fact, Lorentz had four female doctoral students over the course of his career: Geertruida de Haas-Lorentz (a.k.a. Berta), Johanna Reudler, Eva Bruins, and Jo van Leeuwen.

Wait, Jo …. van Leeuwen? Uh oh.

Luckily, I think I can dismiss her as a possibility, because apart from Herzfeld’s vague identification of a “van Leeuwen,” there is nothing else to tie her to Zurich. Moreover, there does seem to be a known photograph of Hendrika Johanna (a.k.a. Jo) van Leeuwen from her profile on the Huygens Institute and she looks nothing like any of the women in the mystery photograph.

You know who does look like one of the women in the photograph of the Weiss lab? The woman second from the right in this picture of one of Hendrik Lorentz’s classes.

Could this woman be Eva Bruins? I was starting to lean toward yes.

Sadly, this project wasn’t done with throwing wrenches in the process and refused to be neatly tied up in a bow. In the course of searching, I discovered yet another identification key for another copy of this same photograph, from akg-images , a commercial image licensing company.

#6 or #9 Tatyana Ehrenfest?

Their identification key differed in some important respects. There were many people left unidentified. Whoever wrote their answer key for instance, hadn’t identified Karl Herzfeld or Frithiof Wolfers. They also misidentified René Fortrat as Pierre Weiss. I could almost be persuaded on the last one – I had thought it was odd that a picture of Pierre Weiss’s lab group did not include Pierre Weiss himself. And Fortrat is seated in the center front, but there are some details that make me doubt that it could be Weiss. For one thing the person depicted is almost certainly too young to be Weiss; Weiss would have been 48 years old at the time of the photograph. For another, the mustache and eyebrows are too neat. (Compare it to the photograph of Weiss above or other known photographs.) People do change their mustaches, but rarely their eyebrow shape so drastically, at least at that time.

The other major difference though gave me great pause. The akg-images image key claimed that one of the women (numbers 6 or 9 above) was actually Tatyana (also spelled sometimes Tatjana or Tatiana) Ehrenfest. Born Tatyana Afanasyeva, she was also a physicist in her own right who worked on statistical mechanics and thermodynamics. Her name is also sometimes listed (e.g. in some of her publications ) as T. Ehrenfest-Afanassjewa. She was born in Kiev, then part of the Russian Empire, and married Paul Ehrenfest in 1904 after they met at the University of Göttingen. Given that she also worked in physics (although she did not hold a paid position as her husband did), it would not be improbable that she could be included in a photograph of laboratory visitors.

But my first step in looking into this claim would be to first determine whether or not she was even present in Zurich in 1913 when her husband was. They had moved to the Netherlands in 1912 when he took up a position at the University of Leiden. When Paul went to visit Zurich in the summer of 1913, did she go too?

While I was investigating the Ehrenfests, I followed up with akg-images and heard back from Jennifer Carding, a Senior Account Executive. She informed me that they didn’t have a record of who had done the original identification for their copy and also that they had decided to update their key to match ETH Zurich’s.

I also reached out to the Boerhaave Museum in Leiden, the Netherlands, which holds a huge collection of personal and scientific archive of Paul Ehrenfest , but did not hear back at least as of the date of the publication of this blog post.

To be honest, I thought it was unlikely that the woman pictured was Tatiana Ehrenfest. I’m really not that good with faces, but a comparison of the photograph I was investigating with a known photograph of Tatiana Ehrenfest like the one above or one available in this Physics Today article made it seem unlikely that she was one of the three women pictured.

Bruins, Frankamp, Ehrenfest… or Rotszajn?

At this point though, I wanted more information. My searching for Eva Bruins and Catherine Frankamp had turned up their mention in the collected Einstein papers , and Johannes Wahl had also pointed me in this direction. A letter from Einstein to Ehrenfest mentions there are Dutch women staying with him, but not their names. Annotations on this letter suggest that they are Eva Bruins and Catherine Frankamp. The Einstein collected papers are online and text searchable, which meant a quick browse and keyword search also turned up Bruins and Frankamp’s mention in the caption of one of the illustrations :

Unfortunately, the illustrations are not viewable online. And this was the first time I had come across Sophie Rotszajn. (Document 457 in the Einstein collection is a postcard from Einstein to Leonid Mandelshtam and signed by participants in a colloquium, including Bruins, Frankamp, and Sophie Rotszaijn.) I wanted to see this picture… Looked like it was time to head to the library.

Living nearby and working closely with the Niels Bohr Library & Archives is a wonderful treat for a historian of physics, and I decided it was finally time to take advantage of their book collection.

First out of curiosity I checked Martin Klein’s biography of Paul Ehrenfest. I discovered that Ehrenfest and Einstein had had a long friendship, and – before he received the professorship at the University of Leiden – Ehrenfest had wanted to move to Zurich. When Paul went to Zurich in the summer of 1913 to visit Einstein, Tatiana did go with him. But it was too much to hope for a mention of the photograph or of Tatiana’s visiting Weiss’s lab specifically.

Instead I learned that Paul Ehrenfest took over as the University of Leiden’s professor of theoretical physics from Hendrik Lorentz - including potentially his supervision of some of Lorentz’s students. Could this explain why the Dutch women are in the photograph in the first place? I did not find a mention of Bruins or Frankamp, but Klein did casually mention the “two van Leeuwen sisters” who were students of Ehrenfest. This was likely Hendrika Johanna (Jo) van Leeuwen and her younger sister Cornelia (Nel) who also earned a master’s degree in theoretical physics under Lorentz.

Next, I turned to Einstein’s collected papers and eagerly opened the volume to find an illustration…. Of the same photograph I had been investigating this whole time. This was somewhat disappointing, although clearly multiple copies of this photo had been made and kept. What was more disappointing was realizing that the caption to the photograph only identified the three women in general as Eva Bruins, Catherine Frankamp, and Sophie Rotszajn. It did not say which was which, and the only evidence to support that assertion seemed to be the signatures on the separate postcard from Einstein to Mandelshtam.

Finally I checked out the Catalogue of the Paul Ehrenfest Archive at the Museum Boerhaave Leiden to see if there was anything I might want to follow up on in the future. (This catalog had been published in 1977, and the collection has since been added to , but it was worth checking out.) There were no letters listed from either van Leeuwen sister, but there was a letter which mentioned a “request” from “Frankenkamp” (likely a misreading of Frankamp) and Bruins dated to around the 1910s. Potentially a request to go to Zurich in the summer? Looking at the photograph again, I notice Frankamp and Bruins are standing on either side of Paul Ehrenfest, from which a tenuous argument could be made that this is to indicate their student status in relation to his as their professor. An interesting possibility.

And as a sidenote, there were also some letters from Anna B. Foehringer in the Ehrenfest collection, who was one of the translators of Chwolson’s textbook - unlike Grigorjeff whom Karl Herzfeld claimed in the original caption to have been the translator. There is nothing else I have found that potentially ties Foehringer to Zurich though.

At this point I was fairly well convinced about Bruins and Frankamp (and about who was who), but I still wanted to follow any lead I could find on Rotszajn. I did find her in a searchable database of enrollments at the University of Zurich , which gave me a great deal of information. She was born in 1873 and enrolled at the University of Zurich (importantly not ETH Zurich) in 1910, eventually earning her doctoral degree in 1920 under Simon Ratnowsky. Her dissertation is available to read online via Google Books in German. The short curriculum vitae at the end of her dissertation corroborates and extends the information available in the matriculation record, and makes it increasingly unlikely in my opinion that Sophie Rotszajn is pictured in the photograph. For one thing, she is not Dutch, she was born in 1873 in Warsaw which was then part of the Russian Empire. (So it’s unlikely she is one of the two Dutch women in the back row of the photograph.) Rotszajn, it turns out, is also her married name; her birth name was Sand. And, in her curriculum vitae, she thanks the list of professors she took lectures from and worked with. Einstein is thanked, but nowhere in the list is Pierre Weiss. If her base of operations for her studies was the University of Zurich, and she didn’t interact with Weiss enough to thank him in her dissertation, what would have brought her to his lab that day to sit in a photograph of people who worked with him?

Conclusion

At this point I’m fairly certain I can offer – at least for now – a somewhat settled key to the photograph.

1. Karl F. Herzfeld
2. Otto Stern
3. Albert Einstein
4. Auguste Piccard
5. René Fortrat
6. A. J. (“Marie”?) Grigorjeff
7. Catherine Frankamp
8. Paul Ehrenfest
9. Eva Bruins
10. Gabriel Foëx
11. Frithiof (Fred) Wolfers

If I were able to go to the Museum Boerhaave and ETH Zurich, it’s likely I would be able to find out more with an in depth look at their archives. Some questions remain slightly unsettled for me. Who took the photograph? Was it Pierre Weiss and that’s why he doesn’t appear? Why did Grigorjeff return to Zurich, and what was her connection to Weiss? And of course, I would feel much better if there were known photographs of all of the women so they could be conclusively identified.

As I was working on this, it got me thinking about what kinds of identities (or identification) do we assume are prone to mistakes, and which not? This was what I often came back to when I was considering which of Karl Herzfeld’s identifications to accept or question. For Herzfeld, nationality seemed fairly stable. He remembered two of the women were Dutch, although he seemed to get everything else from their names to their professions wrong about them. He also remembered that Grigorjeff had worked with Chwolson, and that something in her work had been on the Russian side of Chwolson’s publication process (although again he misremembered her actual role in the project). So he remembered nationalities for the most part. And he remembered names and professions or research specialties…. so long as they were men.

Spelling is not and has never been my strong point. For Herzfeld, a man who worked in multiple languages (and Cyrilic is a whole different alphabet), it was also not. Variations in spelling I was completely expecting, and accepting of. But I was definitely saddened that Herzfeld’s personal memory, and the readily-available historical record, were most forgetful of the women in the photograph. Saddened, but not surprised.

But still, at this point I am content with as much progress as I was able to make. My completionist impulses will never be totally satisfied, but now I can relax … at least until the next “history mystery” catches my attention.

References and Further Reading

Blaauboer, Mirjam. “Leeuwen, Hendrika Johanna van,” in: Digitaal Vrouwenlexicon van Nederland. 27 March 2017. https://resources.huygens.knaw.nl/vrouwenlexicon/lemmata/data/Leeuwen

Catalogue of the Paul Ehrenfest Archive at the Museum Boerhaave Leiden. Compiled by Bruce Wheaton. Communication 151. Museum Booerhave, 1977.

Delft, Dirk van. “Paul Ehrenfest’s final years.” Physics Today 67, no. 1 (January 2014), 41-47. https://physicstoday.scitation.org/doi/10.1063/PT.3.2244

Ehrenfest-Afanassjewa, T. “On the Use of the Notion ‘Probability’ in Physics.” American Journal of Physics 26 (1958), 388-392. https://doi.org/10.1119/1.1996167

F., R. H. Book review of Introduction a l’etude de la physique theorique by Prof. René Fortrat (Paris: J. Hermann, 1927). Nature (23 March 1929), 444.

Feder, Toni. “Ehrenfest letters surface.” Physics Today 61, no. 6 (June 2008): 26-27. https://doi.org/10.1063/1.2947641

“Gabriel Foëx.” Physics Today 16, no. 5 (1963), 106. https://doi.org/10.1063/1.3050907

Ginoux, Jean-Marc. History of Nonlinear Oscillations Theory in France (1880-1940). Springer, 2017.

Klein, Martin J., A. J. Kox, and Robert Schulmann, eds. The Collected Papers of Albert Einstein Volume 5: The Swiss Years: Correspondence, 1902-1914. Princeton University Press, 1993. https://einsteinpapers.press.princeton.edu/

Klein, Martin J. Paul Ehrenfest Volume 1: The Making of a Theoretical Physicist. Amsterdam: North-Holland Publishing Company, 1970.

Kox, A. J. The Scientific Correspondence of H. A. Lorentz: Volume 2, the Dutch Correspondents. Springer, 2018. 846-7.

Kragh, Helge. “Photon: New light on an old name.” Arxiv. Last revised 28 Feburary 2014. Accessed 22 December 2022. https://doi.org/10.48550/arxiv.1401.0293

“Professor at the ETH Zurich (1912-1914).” Einstein Online. ETH Zurich University Archives. Accessed 3 January 2023. https://library.ethz.ch/en/locations-and-media/platforms/einstein-online/professor-an-der-eth-zuerich-1912-1914.html

Vogt, Annette B. “Ehrenfest-Afanas’eva, Tatiana A.” Dictionary of Scientific Biography. Vol. 20. New York: Charles Scribner’s Sons. pp. 356–358.