6. In the case of the interlined groups of two sets of figures, the
first set represents the number of the page; the second set the
number of the line, probably counting from the top, of which line
the required letter will prove to be the initial one.

7. The words thus spelled out by the interlined groups of double
figures are, in all probability, proper names, or other uncommon
words not to be found in their entirety in the book on which the
cryptogram is based, and consequently requiring to be worked out
letter by letter.

8. The book in question is not a dictionary, nor any other work the
words of which come in alphabetical rotation. It is probably some
ordinary book, which the writer of the cryptogram and the person
for whom it is written have agreed upon beforehand to make use of
as a key. I have no means of judging whether the book in question
is an English or a foreign one, but by it alone, whatever it may
be, can the cryptogram be read.

"Now, my dear Ducie, it would be wearisome for me to describe, and
equally wearisome for you to read, the processes of reasoning by
means of which the above deductions have been arrived at. But in
order to satisfy you that my assumptions are not entirely fanciful
or destitute of sober sense, I will describe to you, as briefly as
may be, the process by means of which I have come to the conclusion
that the book used as the basis of the cryptogram was not a
dictionary or other work in which the words come in alphabetical
rotation; and such a conclusion is very easy of proof.