Solving the Mystery of the Cambridge Codes

Dear detectives,

Thank you to the many of you that wrote in by mail and at Dearholmes.com/solve with your questions and solutions to last month’s mystery, “the Cambridge Codes”. We’re evaluating your solutions now, and look forward to naming the mystery’s Featured Detective in the near future. In the mean-time, Holmes would like to share with you a letter he wrote to Watson explaining how he solved the case. Below his letter is a table that will prove helpful to those of you that did not manage to decipher the mystery’s secret codes. If you were stumped, you may enjoy re-reading the first four letters after reading the solution.

Sincerely yours,

The Dear Holmes Team

——

1 August, 1914

My Dear Watson,

Contrary to your previous statement that I would wish for you to “cut the poetry,”  I’ve enjoyed hearing from you over the last few days – initially when I read your letters, and again just a few minutes ago, when I read them again while sitting here in Mycroft’s office. They were a very welcome reminder of good times, and much appreciated after my most recent sojourn as “Altamont,” that irascible character that is perhaps a bit too easy to assume, like a favorite old coat.

Although I couldn’t inform you, I’ve been back in London for several days, but I’m treading carefully in anonymity, as the work of several years is coming to a boil quite soon. As you know, my retirement nearly a decade ago, when I seemingly abandoned my London practice in favor of a life of curmudgeonly beekeeping, was mostly a ruse so that I could be of greater value to Mycroft in his escalating efforts to delay the war. When the Prime Minister himself tasked me a couple of years ago to further increase my efforts, there was really no way to refuse. Taking a leaf from Birdy Edwards, I became Altamont, that cranky Irish-American, and dived in amongst the enemies of our country. Fortunately, in order to assure those who were watching to make sure that Sherlock Holmes was still rusticating in Sussex, and confirm that he was in no way connected to Altamont, I was able to return home for the occasional visit, making appearances as myself, investigating the occasional curious affair that came my way, and most of all, spending time with my old friend Watson.

As you know, previous efforts have been made to root me out, and now, especially at this important date and so close to the onset of hostilities, another attempt was very likely. When Moravčević showed up at your practice with his curious messages, it seemed that this was their latest ploy. You informed Mycroft, as previously instructed, and he in turn researched your curious Serbian acquaintance, as well as aspects of his story. The man’s bona fides didn’t hold up, and he was quickly identified as a foreign agent, apparently using these complex messages to intrigue me, naming locations in London where I might be expected to show up after decoding them. Needless to say, I was not able to oblige him, so they tried several times. (I should mention that Professor Dunbarton is completely above suspicion, and in fact Mycroft was able to determine that he never copied or erased anything from the Cavendish Laboratory blackboards – it was all contrived by Moravčević from the beginning.)

Moravčević hoped that I would be intrigued and reveal myself. He knew that I would be able to decode the messages quite easily, based on my realization that Cavendish is Cambridge’s physics laboratory. The initial line in each message was quite obviously some sort of chemical equation, but set up in such an absurd way that those various elements could never combine in nature. Clearly it was a simple alphabet substitution, designed for me to easily interpret. If one examines the first twenty-six elements of the Periodic Table, (mostly recently codified about a decade ago by Mendeleev  – thus my hint to you!) and then assigns a corresponding letter, the initial code is quite simply understood. For instance, in the first message, the C (for Carbon) is the sixth element, and F is the sixth letter in the alphabet. CFHePSiHLi2F then spells Fibonacci, also known as “The Golden Ratio,” a very famous series of numbers. (As you know, it became a necessity for me to gain a deeper understanding of mathematics when I was preparing myself to face Professor Moriarty.)

I assigned letters to these Fibonacci numbers, in order, taking into account that B and C are both the number 1, and then matched the numbers on the second line of the message, which spelled NELS COL – or, as is obvious to any Londoner, Nelson’s Column – and Sun for Sunday at noon. (Of course, in the word Fibonacci, there are two C’s, and since one doesn’t repeat an element in even a ridiculous chemical equation,  the subscript 2 was used for double letters.)

Since the day after you received the message was Saturday, it was clear that the meeting was planned for the next day, and thus I directed you to be there. Moravčević’s agents were watching to see if I also showed up, and Mycroft’s men were in place to keep an eye on them. Each of them was successfully followed, and later apprehended, and they will soon be tried for espionage.

The subsequent messages worked much the same way. The second absurd chemical formula, PBe2, spelled Odd, which – considering that the first code referred to a famous increasing number sequence – could only mean odd numbers. (They couldn’t use famous sequences like Archimedes’ Pi or Euler’s Number, which have repeating digits instead of increasing, as the possibilities would be too complex to easily solve.)

Using the first twenty-six odd numbers, matched to letters, gave us the corresponding message: BLMSB SQU GDN TUES NOON, or Bloomsbury Square Garden, Tuesday Noon. Likewise, the third chemical formula, SArFAlB, spelled Prime, and the first twenty-six prime numbers referred you to KNGS BNCH WLK, or King’s Bench Walk on Thursday at noon. At each of those meetings, Moravčević’s men were lurking about, and again Mycroft’s people – many more than you might have noticed or realized – were also in attendance, watching and gathering information. (I’m including a copy of the codes that I’ve jotted down for you to work it out yourself.)

Needless to say, with the knowledge that Britain will soon declare war, there was no need to let this play out any longer, and Moravčević has been taken into custody. I have just been downstairs to look in on the interrogation, and he is happily spilling everything that he knows. (Luckily the Kaiser has, more often than not, recruited some particularly spineless and often stupid agents. Still, I don’t naively expect that this will make things any shorter or less painful over the coming years – and I believe that it will be years rather than months, as some optimists incorrectly forecast.)

In any event, my time as Altamont is running out quite quickly. In some ways, I rather feel that the fellow resembles the old year on New Year’s Eve as the last sand dribbles through the hour glass. But there is one bit of business left, and for that, I would request your assistance. I – or rather Altamont – has an appointment with Von Bork (of whom you are aware) tomorrow night at his home on the Essex coast. I understand that he will be claiming some kind of diplomatic immunity and intends to return to Germany. We will prevent that, as he’s already too close to figuring out that all the false information provided to him by Altamont is simply smoke. He must be taken off the board before he can educate his masters, and as Altamont, I am best suited to approach him and effect his arrest, giving him the impression that he will still be allowed to leave diplomatically, instead of being treated as the spy that he is. If you could bring an automobile and meet me in the village near Von Bork’s estate tomorrow at about five in the evening, it would be much appreciated. After some catching up, we’ll proceed about our business.

I’m sure that you have further questions, and I’ll attempt to answer them while we grab a little supper tomorrow and wait for our scheduled visit with the German spymaster. It will be good to you see you again, my dear Watson, and just like old times.

Very best,