e be a numerical key concealed in
that? My dear Gregory,' said Mr Somerton, laying his hand on his friend's
knee, 'that _was_ the key. I didn't get it to fit at first, but after two
or three trials I saw what was meant. After the first letter of the
inscription you skip _one_ letter, after the next you skip _two_, and
after that skip _three_. Now look at the result I got. I've underlined
the letters which form words:

[D]R[E]VI[C]IOP[E]D[M]OO[M]SMV[I]V[L]IS[L]CAV
[I]B[A]SB[A]TAO[V]T
[R]DI[I]EAM[R]L[E]SI[P]VSP[O]D[S]EE[I]RSE[T]T[A]
AE[S]GIA[V]N[N]R
F[T]EEA[I]L[N]QD[P]VAI[V]M[T]LE[E]ATT[O]H[I]OO
[N]VMC[A]A[T].H.Q.E.

'Do you see it? "_Decem millia auri reposita sunt in puteo in at_ ..."
(Ten thousand [pieces] of gold are laid up in a well in ...), followed by
an incomplete word beginning _at_. So far so good. I tried the same plan
with the remaining letters; but it wouldn't work, and I fancied that
perhaps the placing of dots after the three last letters might indicate
some difference of procedure. Then I thought to myself, "Wasn't there
some allusion to a well in the account of Abbot Thomas in that book the
'_Sertum_'?" Yes, there was; he built a _puteus in atrio_; (a well in the
court). There, of course, was my word _atrio_. The next step was to copy
out the remaining letters of the inscription, omitting those I had
already used. That gave what you will see on this slip:

RVIIOPDOOSMVVISCAVBSBTAOTDIE
AMLSIVSPDEERSETAEGIANRFEEALQD
VAIMLEATTHOOVMCA.H.Q.E.

'Now, I knew what the three first letters I wanted were--namely,
_rio_--to complete the word _atrio_; and, as you will see, these are all
to be found in the first five letters. I was a little confused at first
by the occurrence of two _i_'s, but very soon I saw that every alternate
letter must be taken in the remainder of the inscription. You can work it
out for yourself; the result, continuing where the first "round" left
off, thus:

_rio domus abbatialis de Steinfeld a me, Thoma, qui posui custodem
super ea. Gare a qui la touche_.

'So the whole secret was out:

"Ten thousand pieces of gold are laid up in the well in the court of
the Abbot's house of Steinfeld by me, Thomas, who have set a guardian
over them. _Gare a qui la louche_."

'The last words, I ought to say, are a device which Abbot Thomas had
adopted. I found it with his arms in another piece of glass at Lord
D----'s, and he drafted it bodi