be identified.

If any one wishes to get a thumb-print impression without the
suspect's knowledge, simply hand him a piece of paper, asking him to
identify it or examine it for one reason or another, afterwards
sprinkling some special black powder over it which brings out the
impressions as clear as life. Another sort of white powder is used for
bringing out impressions on glassware.

Once the impression is secured, the fingers are classified according
to a regular plan. The lines on them are divided into loops, whorls,
arches, and composites, the latter class made up of a collection of
the first three. Each pair of fingers as the index, little and ring
fingers has a special valuation which is used to identify them and
facilitate classification. One pair will be classified according to
the number of little ridges between the delta, or point where all
bifurcate, and the outer ring. If there are more than nine on one
finger, it is classed as an over-nine.

It is seldom that two similar fingers are alike and the other finger
usually would be an under-nine finger, say six. So there is the first
pair classified thus, 9-6. The next two fingers may have rotary lines
and are merely classified as R, the next two may not have many lines
at all that will count, so are marked 0, while perhaps the last pair
is unmatched, a point being allowed to one and nothing to the other.

Thumb or finger-prints are absolutely serviceable and certain in the
detection of crime or in establishing a person's identity.

That this system may be most effectively employed as an adjunct to the
rogue's gallery for fixing the identity of criminals there can be no
doubt, since, from various experiments made it has been demonstrated
that impressions made from the dermal furrows of the thumb or finger
of no two persons can be sufficiently identical, when inspected under
a microscope, to be mistaken one for the other; and that it is a
powerful agency for the detection of criminals.

Very often, on the scene of a crime, finger marks are found on glossy
surfaces (bottles, glasses, window panes, door plates, painted and
varnished walls, etc.). By a comparison of such impressions,
photographed by a special process, it is easy either to discover the
maker of the finger marks observed at the scene of the crime, or to
establish the innocence of a suspected person whose digital
impressions have nothing in common with those marks.

Note and study fac-simile imp