M – Magic Mirror

“Mirror, Mirror, on the wall, who is the fairest of them all?”

– The Evil Queen, Snow White

Yeah, no, not that Magic Mirror.  Nor yet the one from the Shrek films.  This one is quite good, but still, no.

I think I may have mentioned that I quite like tosh films.  The Mummy falls squarely into the really good fun, but complete tosh category – definitely worth a watch (or three or five), but isn’t really going to do anything for your intellect or soul.  Again, as I think I may have mentioned before, it’s the clever little details that turn something from being completely mindless to quite good fun.  One of the little details in The Mummy is the scene where the adventurers light up a room using large copper mirrors to reflect sunlight into the underground space.  Probably the best thing here is to close that image with the Mythbusters assessment: plausible but ridiculous.  But it does give us a nice starting point for today’s post.  Big coppery mirrors.

I’m drifting slightly from the main fare of speculative fiction and into the realms of detective fiction, but, paraphrasing Isaac Asimov quite a lot, s.f. is very rarely, if ever, just s.f.  It’s invariably s.f. and something else.  Similarly, detective fiction doesn’t just have to be detective fiction.  So we can use the description of a scene in middling-good film, to describe a particular well-loved detective – for all the great respect that I have for Sherlock Holmes, the stories are for the most part plausible but ridiculous.   On reflection (sorry), that may be a description that can be used more widely in the genre, but we’ll leave it there for the time being.  A phrase that crops up from time to time (and one that has even been used to sell books and TV series) is the ‘Rivals of Sherlock Holmes’.  Holmes is the detective with the good PR – today he is the one that is remembered, he is the one that has had the countless spin offs, adaptations, reboots.  In the same way that people will point to a particular actor in the role of Dr Who and say ‘he was mine’, so people will look at a particular portrayal of Holmes, and say ‘Yes! That is how Holmes is meant to be!”.  (Although in the case of Holmes, maybe it is the portrayal of Watson that is more important to the felicity of the adaptation.  In a strange way, I do think that Martin Freeman is perhaps the best Watson, certainly more so than Holmes he is paired with).

There are many rivals, and it is a shame that more are not remembered and celebrated.  Some are truly excellent and certainly on a par with the detective that they are being compared with.  These rivals appear in a period of time between the 1880s and 1920s, with some having careers running into the 1930s and 1940s.  One, who in some ways out Holmes’ Holmes is Dr John Thorndyke, a medical doctor who steps into the field of Medical Jurisprudence, to the extent that he becomes a fully qualified lawyer, even passing the bar.  Whilst he does appear in court, his usual modus operandi is to have someone else conduct the case on his behalf so that he can appear as an expert witness, having brought a scientific approach to the case and solved it by assuming nothing a priori, and never believing that his interpretation is the only possible one – until he has all his ducks firmly in a row.  I can thoroughly recommend the series to those interested in the time (the early 20th century) and in detective stories.  As someone reading them around 100 years later, there are all sorts of issues, but these stem more from the author’s personal beliefs than they do from anything else.  But today is not intended to be a critique of the author (R. Austin Freeman) or his creation, except where such a critique helps to understand magic mirrors.

The Magic Casket is a typical Thorndyke story: he stumbles into the beginning of a mystery whilst out walking with his friend and ‘Junior’ Christopher Jervis (another doctor, a few years younger than Thorndyke who has been inveigled into the medical jurisprudence line).  They find a bag with some bits and bobs in, one of which happens to be a small “Chinese/Japanese box”.  Handily the bag has the address of the owner, who lives not very far away and they go to return it, becoming embroiled in robbery, murder and mayhem.  One of Freeman’s favourite motifs is that of the treasure-hunt, especially if it can be linked to some poor young(ish) person who has been done out of their rightful inheritance.  In this instance, the unfortunate at the heart of the story is a young lady who’s father was the victim of a robbery that led to him becoming more or less bankrupt.  By a series of chances which are, shall we say plausible, but ridiculous, the young lady comes into possession of the Chinese/Japanese box, which contains the treasure map.  But this is no ‘X marks the spot’ affair, at least not exactly – no mouldering parchments (this time, anyway) for Austin and Thorndyke.  No, instead it is the box itself that is the key – although it takes the uncanny mind of Thorndyke to unravel the problem.

Another of Austin’s predilections is for the incorporation of the latest research and development of techniques, where such might be of use in his story.  To this extent, there is one story that, to my mind, becomes faintly absurd in the actions of one of the main characters in order that a particular plot point be allowed to work.  However, in The Magic Casket, the plot device is not only completely integrated into the plot, but is actually plausible and doesn’t interfere with anyone’s capacity for rational thought.

We’re pretty used to hearing about the intellectuals of the Far East having discovered things a long time before we got to it in the West.  Magic mirrors are no exception – records from around 1100 AD suggest that the technology was already old then and a venerable manuscript which is purported to explain the mysteries of these devices is known to have been lost some time before this.  So what’s magic about them?  Well, let’s imagine you’ve got a piece of metal that has a design beaten or punched into it one side and is polished to a mirror finish on the other.  If you catch the light with it properly and reflect that light onto a painted wall (or something with a decent finish), you will see the reflection of the image on the reverse side.  For a long time it was not understood exactly how this could occur.  The ancients seemed to have some idea that light was passing through the metal of the mirror, although they seemed to have no reasonable explanation about why this might be the case.  So what is really going on?  Well, to start with, this only works if you have an annealed piece of metal, that is to say one that is relatively soft.  It also needs to be relatively thin – not too thin, or you’ll end up bending the piece whilst you are working on it, but thin enough that when you start to introduce the design, you harden the material all the way through the metal.  Hardening is a well understood process and one that occurs in a wide variety of situations, some of which are advantageous and some more problematic.  When you take your piece of metal out of the heat, it usually comes out with a certain microstructure, which will contain a number of defects.  These defects are at the atomic level, so for example if you have rows of atoms stacked up, you might have a row that is only half complete, or one in which there is an atom missing.  If you move these defects around – by hitting the metal – then they interact and you can strengthen the metal.  But in doing so you have plastically deformed the metal, you have introduced non-recoverable change.  This might be a good thing for something where a particular property is required, but equally it might be completely undesirable where you had the properties you wanted and changed them when you machined a billet of material into shape.



A Bonus(?) Mystery(?) – Who gave Freeman the idea?

Potentially there is one final mystery that could be attributed to the story.  The Magic Casket was published in 1927, and the fount of all knowledge, Wikipedia, suggests that William Bragg (yes, the Sir William H. Bragg, OM KBE PRS and Nobel Laureate) explained the effect in 1932, the problem having baffled the leading (Western) minds of the previous century.  The romantic (in the original sense of the word) solution would be to imagine Freeman sitting in a Royal Society lecture given by Bragg sometime before either published their books, with Freeman’s coming some five years earlier.  However, the slightly more prosaic solution (albeit one that appeals to an academic with sleuthhound tendencies) is that the Wikipedia article, which is actually fairly well referenced, is itself based on a poorly researched article.  One of the references, which is available as a .pdf straight off the wiki-page, gives the Bragg attribution, but no reference, so in some ways the trail goes cold.  However, towards the end of the story, Thorndyke demurs that he has shown any especial brilliance as “the effect was demonstrated by Professor Silvanus Thompson, several years ago”.  Silvanus Thompson was another ‘big brain’ of the time.  At this remove it is difficult to compare the two except by the obvious measures of their success.  Thompson, whilst not achieving the same heights as Bragg was a popular educator, and whilst he may never have been a President of the Royal Society, he was an FRS and the first President of the British Radiological Society, and is one of very few people to have a book written a hundred years ago that is still actively in print today.  So, to some extent, our romantic solution still stands, but we have Thompson delivering the lecture (in 1897).  However, life is rarely as simple as we would like.  The internet is a wonderful thing (in some ways), and I was able to relatively easily find a publication by Alan Mills1, which points out that Thompson was not the first to investigate the problem, nor yet to propose a solution, although it is probable that he did answer some of the issues that were left unaddressed by Ayrton and Perry in 1878.

1Mills, A; Magic Mirrors, Physics Education, 46, (2011), pp 595-598 doi: http://dx.doi.org/10.1088/0031-9120/46/5/014


7 thoughts on “M – Magic Mirror

  1. I wonder if those “magic mirrors” are still made today? Metal on one side, polished on the other, and reflecting an image onto another surface. Perhaps it’s similar to projectors.

    Either way, it sounds cool. Great post. Well-written. Keep it up!


    1. Hi Hilary,
      It’s not an obvious one. One way to think about is if you had one of those blocks made of a number of pins that you press your hand into and it leaves an imprint behind. Now imagine that you are able to remove an infintesimal amount from the pins that are left sticking up, and then you flatten it all out again. If you catch the light right, you’ll see the imprint of the hand, but otherwise you won’t be able to tell.

      Sherlock is an odd one. I think it is a good update in many ways, but it has drifted quite a lot recently.


  2. In your discussion of the Coppery Mirror, you’ve certainly hit on some points to mull. I was especially taken by the PR angle. You can’t think detective without Holmes and Watson popping up in the margins of your brain. I love the mystic of mirrors. The Chinese had a ritual of breaking a mirror in half when a mate died, believing that when the second passed, s/he would find the departed loved one and make the mirror whole again.

    I’m giving you little shout out tomorrow. I’m enjoying your blog posts during the AtoZ madness!

    Liked by 1 person

    1. Thanks for dropping by and for the thought provoking comment. It’s important to remember the social side of these things, the human touch (even if you are trying to focus on the technological!). Glad you are enjoying the posts – hopefully the second half of April will be as good! (Thanks, too for the shout out).


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