"But he forgot that after he had brought out the red writing by the
use of the sulpho-cyanide, and though he could count on Vera Lytton's
placing the note in the jar of ammonia and hence obliterating the
writing, while at the same time the invisible writing in the mercurous
nitrate involving Dr. Dixon's name would he brought out by the ammonia
indelibly on the other side of the note--he forgot"--Kennedy was now
speaking eagerly and loudly--"that the sulpho-cyanide vapors could
always be made to bring back to accuse him the words that the ammonia
had blotted out."

Before the prosecutor could interfere, Kennedy had picked up the note
found in the ammonia-jar beside the dying girl and had jammed the
state's evidence into the long-necked flask of sulpho-cyanide vapor.

"Don't fear," he said, trying to pacify the now furious prosecutor,
"it will do nothing to the Dixon writing. That is permanent now, even
if it is only a tracing."

When he withdrew the note, there was writing on both sides, the black
of the original note and something in red on the other side.

We crowded around, and Craig read it with as much interest as any of
us:

"Before taking the headache-powder, be sure to place the contents of
this paper in a jar with a little warm water."

"Hum," commented Craig, "this was apparently written on the outside
wrapper of a paper folded about some sal-ammoniac and quicklime. It
goes on: