From the Father Brown story "The Blue Cross":

It was he who had kept up an unaccountable and close correspondence with a young lady whose whole letter-bag was intercepted, by the extraordinary trick of photographing his messages infinitesimally small upon the slides of a microscope.

What is the "trick" being described here? I don't understand what it is or how it works.


2 Answers 2


He made very, very, very small letters, on microscope slides. These were sent to the young lady in question, who used a microscope to read them.

  • Thank you. I didn't get that the recipient of the micro-messages was the young lady (I thought that the unaccountability was paart of the trick, not the result.) Apr 3, 2021 at 8:09

"The Blue Cross" was the first Father Brown story, published (according to Wikipedia) in 1910.

The technology of photo microdots had been known for some decades by then.

  • 1
    Could you explain what photo microdots are, and how they relate to the story? We prefer answers to be self-contained.
    – bobble
    Mar 26, 2021 at 19:53

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