Thumb-marks may be generally classified as loops, arches and ovals, or
whorls; the ovals irresistibly remind one of whirlpools as well as the
volutions of shells, while the majority of loops or arches resemble in
their convolutions the rapid movement of rushing water.

Thumb-print identifications have been extended to commercial uses by
the postal savings bank on the Philippines at Manila. This bank has
recently issued a series of stamp deposit cards, on which are spaces
for stamps of different values to be affixed. When the depositor has
stamps to the value of 1 peso (50 cents) on the card it is exchanged
at the bank for a deposit book, showing the amount to his credit.
Opposite the lines for the owner's signature and address is a square
ruled off for the reception of his thumb-print, so that even if
illiterate, depositors may readily 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