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or the direct sunlight than the other, and some of the colour- 
ing matters present may thus have been more or less altered 
or destroyed. One person may have a habit of leaving his 
steel pen in the fluid, so that some of the iron may be dis- 
solved, thus altering the character of the ink, whilst the 
other may not do so, or may employ a quill in writing. 
Again, some persons may allow their inks to dry up to a 
certain extent and then add to them any fluid which may 
be at hand, such as tea, coffee, wine, beer, water, &c., each 
of which would alter the character of the writing fluid, 
whilst others may use mixtures of two or more different 
inks, in different and characteristic proportions. One can 
therefore understand that many persons may have in their 
ink-bottles fluids which are so peculiar in chemical compo- 
sition that they may have as much individuality about them, 
when treated with reagents, as the faces of their owners. I 
have tested the same ink on different kinds of paper, and 
the resulting shades of colour produced were identical in 
each case. 
To make use of this mode of investigation it would be 
necessary to get the ink or inks used by a suspected person, 
or preferably some writing made by him at or about the 
same time as any letter or document in question and test 
the two side by side with each other. The resulting shades 
of colours may agree precisely and may thus tell strongly 
against the suspected person, or they may differ very much 
and so point towards exonerating him. 
A case lately occurred in which the expert M. Chabot was 
called and gave evidence to the effect that the handwriting 
in a certain libellous letter was that of the person who was 
indicted as the writer of it. As a witness for the defence 
another person came forward and swore that he was the 
writer of the letter in question, and on that evidence the 
case was dismissed. One can, however, under some circum- 
stances, understand that a suspicion of such a witness 
