Buffon’s needle

As a result of recent moves, the (almost) complete set of Buffon’s monumental Histoire naturelle belonging to my father’s family has recently arrived here in Zürich (it comes from my grand-father, who was director of the Muséum d’histoire naturelle de Nantes). I will keep these in my office for the moment, as it definitely lends it a very scholarly air…

(As far as I can see from the web page above, what is missing from our set is the Histoire naturelle des poissons, which was not written by Buffon anyway, but by the Comte de Lacépède, who also wrote the volumes about snakes, which we do have).

Many probabilists know Buffon for his annoying habit of dropping needles on the parquet, and finding the value of π after doing this sufficiently many times. This game was indeed included in his natural history, more precisely in the Essai d’arithmétique morale (or “Essay of moral arithmetic”) in Volume VII of the Suppléments — at least, it is there in my family’s edition, though it is missing from the web site containing Buffon’s works, where the Essai is in Supplement volume 4.

Here are pictures of the first pages of the description of the problem (click for readable larger picture):

Buffon’s needle


Buffon’s needle, 2

Notice the delightful typography and orthography: the “s” that looks like an integral sign (and is barely distinguishable from an “f”), the way the past tense is written demanderoit instead of the current demanderait, etc.

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I am a professor of mathematics at ETH Zürich since 2008.

7 thoughts on “Buffon’s needle”

  1. “demanderait” or “demanderoit” is a “conditionnel”, not a past tense.

  2. Oups, of course! Thanks for the correction…
    But the “oi” does appear in many other places instead of “ai”, not only in the conditional tense. Although I don’t see any in the two pictures above, I’ve just looked in the same volume and found “connoissons” instead of “connaissons” on page 157, “étoit” instead of “était” on page 60, etc.

    (On the first picture above, on may also notice “héxagone” instead of the current “hexagone”).

  3. Sorry for the petty nit-picking: “qui aime bien châtie bien” and I’m a great admirer of your blog (and of your pastiches.)
    By the way, how come you know English so idiomatically?
    And why do you spell “kowalske” in the comment section?

  4. > By the way, how come you know English so idiomatically?

    A lot of reading, mostly (and writing, and living a certain amount of time in the US)…

    > And why do you spell “kowalske” in the comment section?

    That was actually a bizarre setting of the ETH blog software; I think it’s changed now to something more functorial.

  5. Here’s a correction to what I wrote: the needle problem is in the online version of the “Histoire naturelle”, see


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