38 
by alternately dripping in dry plaster and moistening 
with water until the cast is thick enough to withstand 
rough handling. This is the only method of cast making 
used by the more experienced investigators. 
Little of value is in print on the preceding methods of 
recording footprints. A large part of the above has been 
determined by original experiments, and quite as much 
that is new can be learned in almost any line of this work 
by anyone who will experiment for himself. It is hoped 
that many law-enforcement men will try experiments in 
some line of the work and report results for the benefit of 
all. 
If it is not feasible to secure the footprint itself or a cast 
of it, the best remaining method is to photograph the track. 
The camera lens must be exactly parallel to the surface 
photographed, to avoid distortion of perspective. This 
can be done most conveniently by the aid of a clamp for 
attaching a camera to a board or other similar support at 
any required angle. For use in court the photograph can 
be enlarged to the exact size of the original tracks. If in 
photographing, however, a rule is placed alongside the 
footprint, the scale of measurement will appear in the 
photograph itself, regardless of the size of the latter. 
If no better method is available, draw an exact diagram 
of the track, on cross-section paper if possible. For meas¬ 
urements use two lines at right angles through important 
detail points of the track, and parallel to cross-section 
lines. The perpendicular distances from any point to 
these respective lines will then fix its position absolutely. 
Fingerprints .—Few persons are acquainted with the 
value of fingerprints as evidence. They are very valua¬ 
ble where they can be obtained, give absolute identifi¬ 
cation, and are easy to use. They are produced by the 
oily impression of the minute ridges on the surface of the 
skin, and are left even when hands are clean, although very 
faint when the skin is dry or immediately after washing 
it with soap. Fingerprints may be found on anything a 
man handles which has a smooth enough surface, such as 
papers, cans, bottles, and drinking glasses, if they have 
not been obliterated by subsequent handling; and they 
