s is
not done the paper deteriorates, becoming brittle and crumbly. A tray
of distilled water may be used for rinsing or a tray of ordinary tap
water changed several times during the rinsing. The specimen is then
laid out flat to dry.

Wrinkles, such as are left in paper after ordinary drying, may be
prevented by ironing with a moderately hot iron. An electric iron with
a temperature control is desirable. If kept too hot it will scorch or
wrinkle the paper somewhat. The bottom of the iron should be clean so
that unremovable smudges will not be left on the paper.

No ill effects have been noted from working in the 2-percent mercuric
nitrate solution with bare hands for very short periods, but it is a
caustic solution and it is suggested that the specimens be handled
with tweezers or that rubber gloves be worn if contact is prolonged.

CHAPTER XV

_The Use of the Fingerprint Camera_

If a fingerprint is visible, an effort should be made to photograph it
before any attempt is made to develop it. In every case a print
developed with powder should be photographed before lifting. It
sometimes happens that the print does not lift properly although it
may be quite clear after development.

The camera which is especially adapted to the purpose and which is
easiest to handle and operate is the fingerprint camera, one type of
which is shown in figure 424. This camera has several advantages in
photographing fingerprints:

It photographs the prints in natural size.
It contains its own light source.
It has a fixed focus.

Cameras of this type are available in models operated by batteries and
110-volt current. It is believed that the battery-operated type has
the greater utility, since house current may not be available at the
crime scene. When not in use the batteries should be removed as they
will eventually deteriorate and corrode the brass contacts in the
camera.

[Illustration: 424. The fingerprint camera.]

The camera is of the box type and has three button controls which will
open: (1) The metal flap covering the aperture, (2) the front portion
of the frame providing access to the self-contained light bulbs, and
(3) the camera in half, providing access to the batteries and the
shutter as shown below in figure 425.

[Illustration: 425. Button controls permit access to bulbs, batteries,
and shutter.]

A 2-1/4 x 3-1/4 film pack adapter or a 2-1/4 x 3-1/4 cut film holder
holds the film in th