any other assistant than a powerful magnifying glass.

If the ink is very faint, the simplest and most harmless restorative
is sulphate of ammonia, but its loathsome smell once encountered is
not easily forgotten. The experiment in consequence is very seldom
repeated for the result is scarcely good enough to risk a repetition
of so horrible a smell.

The writing on old and faded documents may be restored, by chemical
treatment, turning the iron salt still remaining into ferrous sulphate.
A process which will restore the writing temporarily is as follows: A
box four or five inches deep and long and broad enough to hold the
document, with a glass, is needed. A net of fine white silk or cotton
threads is stretched across the box at about one half the depth. Two
saucers containing yellow ammonium hydrosulphide are placed in the
bottom of the box. By means of a clean sponge or brush, moisten the
paper with distilled water; then place it on the net with the writing
side down. The action of the vapor of the ammonium hydrosulphide will
cause the obliterated writing to slowly turn brown, then black. But
within a short time after removal from the box the writing will again
disappear.

Another method is to wash the document carefully in a solution of
hydrochloric acid, one part, and distilled water, one hundred parts.
Dry the moistened paper somewhat, leaving it just moist enough to hold
a uniform layer of fine yellow prussiate of potash. A plate of glass
with a light pressure should be placed on this. In a few hours dry the
paper thoroughly, and carefully brush off the yellow prussiate of
potash. The writing should come out a Prussian blue. This restored
writing will be permanent unless exposed too much to the light.

The hydrochloric acid must be thoroughly removed; otherwise, it will
destroy the paper. Crystallized soda, two parts, and distilled water,
one hundred parts, in solution, will counteract the hydrochloric acid,
if the document is allowed to float on it for twenty-four hours.

CHAPTER XIV

DETECTING FRAUD AND FORGERY IN PAPERS AND DOCUMENTS

Infallible Rules for the Detection of Same--New Methods of
Research--Changing Wills and Books of Accounts--Judgment of the Naked
Eye--Using a Microscope or Magnifying Glass--Changeable Effects of
Ink--How to Detect the Use of Different Inks--Sized Papers Not Easily
Altered--Inks That Produce Chemical Effects--Inks That Destroy Fiber
of Paper--How to Test Tampered or