"For instance, I have counted the number of threads to the inch in
the ribbon, as shown by the letters of this note. That also
corresponds to the number in one of the three ribbons."

Kennedy laid down a glass plate peculiarly ruled in little
squares.

"This," he explained, "is an alignment test plate, through which
can be studied accurately the spacing and alignment of typewritten
characters. There are in this pica type ten to the inch
horizontally and six to the inch vertically. That is usual.
Perhaps you are not acquainted with the fact that typewritten
characters are in line both ways, horizontally and vertically.
There are nine possible positions for each character which may be
assumed with reference to one of these little standard squares of
the test plate. You cannot fail to appreciate what an immense
impossibility there is that one machine should duplicate the
variations out of the true which the microscope detects for
several characters on another.

"Not only that, but the faces of many letters inevitably become
broken, worn, battered, as well as out of alignment, or slightly
shifted in their position on the type bar. The type faces are not
flat, but a little concave to conform to the roller. There are
thousands of possible divergences, scars, and deformities in each
machine.

"Such being the case," he concluded, "typewriting has an
individuality like that of the Bertillon system, finger-prints, or
the portrait parle."