Naball wrote "t--e."
"The third letter of the cypher, and the second of the proper word, is 'h'--put that next the 't;' and the fourth letter of the cypher, and third of the proper word, is 'e'--place that at the end also."
Naball added two letters as instructed, "t,h--e,e."
"Now," said Eugénie, "there's only one letter left, which must naturally be in the middle."
Naball finished his writing thus: t-h-r-e-e.
"That is three," he said, with a cry of triumph. "By Jove! Miss Rainsford, you are clever; let's make certain, by trying another letter."
"Take 's-s-t-e-o-n,'" suggested Ezra.
Naball wrote the letters as follows:--
s -- s
t -- e