[Illustration: _Another example of this method of making secret plans
is shown here._
_This sketch was made, giving all the particulars that I wanted. I
then decided to bury it in such a way that it could not be recognised
as a fortress plan if I were caught by the military authorities.
One idea which occurred to me was to make it into the doorway of a
cathedral or church, but I finally decided on the sketch of the moth's
head. Underneath in my note-book I wrote the following words:--_
"_Head of Dula moth as seen through a magnifying glass. Caught
19.5.12. Magnified about six times size of life." (Meaning
scale of 6 inches to the mile.)_]