manner there has accumulated since 1901, when the system was
first put in force, a collection of more than two hundred thousand
prints. It is all a matter of system, of scientific and literal
exactness, and there is no margin of error. A mistake in identification
by finger-prints is literally impossible.

As everyone knows, the ridges at the tips of the fingers maintain their
formation from birth to death, and even after. Nothing can change them.
It is a possibility, though I believe it has never been known to happen,
that there are two people in the world who have the markings on one
finger-tip exactly alike. But even that incredible chance is guarded
against, by taking the markings of the whole ten fingers. It will be
realised how great a miracle it would be for two persons to have exactly
the same lines, broken in exactly the same way, in exactly the same
order on their two hands. That fact is the root principle of the
finger-print work.

It is necessary to point out that the existence of the department is
not so much for the purpose of detecting crime as of detecting
criminals. In the administration of justice a judge takes the past
career of a prisoner into consideration when passing sentence. The main
work of the department is to furnish the clue to a past career by
scrutinising the finger-prints of persons on remand to discover whether
they are habitual criminals or not.

A thousand aliases will not help a man, no change of appearance, no
protestations of mistake, if his prints correspond with those in the
files. But it is all so simply done. There is nothing spectacular,
nothing imposing about the process. Practically all that is needed is a
piece of tin, some printer's ink, and a sheet of paper. Within a few
minutes afterwards his record can be known.

Compare this with the old Bertillon system of anthropometric
measurements. Bertillon's system depends on the fact that after a person
reaches maturity certain portions of the body are always the same in
measurement. The theory is sound, but the difficulties in the way of
applying it are immense.

In his book Sir Edward Henry has pointed out the defects of the system.
The instruments are costly, measurers have to be specially trained, and
even so may make a mistake--an error of two twenty-fifths of an inch
will prevent identification--the search among the records may take an
hour or more, and, moreover, through carelessness or inattention, the
whole data may