Page:Popular Science Monthly Volume 89.djvu/87

Rh sorted. Of two cars similar in other respects, for instance, one may have three oblique ventilators while the ventilators of the others are vertical. If no other car possessed a similar mark, it would constitute a factor. Such factors may be found on any part of the car: mud-guards, headlights, radiators, hoods, gas tanks, tire carriers, springs and so on.

To simplify the system, the car is compared with a human being, and the patrolman is taught to identify it from three angles; face, profile and rear. Furthermore, since he recognizes each make by the factors, the trained patrol-man makes a better identification for police purposes than would be possible for even the most experienced chauffeur, since he can swear to his evidence. He can cite the factors he observed as proof, whereas the chauffeur, though equally certain of his case, has nothing to support his decision as a rule except general facts. True enough in itself, nevertheless the cross-examining lawyer can make such evidence almost worthless.

In watching for a certain car in the traffic the patrolmen are taught to use the factors for rapid elimination, after Sherlock Holmes' famous precept of "observation, knowledge and deduction." If the car in question has a crown mudguard, for instance, one glimpse of a flat or oval mudguard is sufficient information. He drops the machine at once. Observing the remaining cars, or those with crown mudguards, he finds contradictory factors in all except the one he seeks.

All of the outlet posts of the city are connected with a single alarm system, and the descriptions of stolen cars, cars containing escaping criminals, or those wanted for any other reason, are communicated as soon as the crime is reported. The importance of training these outlet men to know the various makes is obvious. Eventually every man on the force will receive some instruction along these lines, and a short course has already been incorporated into the schedule of training for recruits.

Note the face, eyes and ears of these cars and how they differ from one another

An escaping machine can be identified by the position of the tail-lights

The "nose" of an automobile is a good index to its lineage