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Page:Popular Science Monthly Volume 89.djvu/87

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Popular SeicJice Monthly


��sortcil. Of two cars similar in other re- spects, 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 an>- part of the car: mud- guards, headlights, radiators, hoods, gas tanks, tire carriers, springs and so on.

To simplify the s\stem, 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 chauf- feur, since he can swear to his evi- dence. He can cite the factors he observed as proof, whereas the chauf- feur, though equal- ly certain of his case, has nothing to support his de- cision as a rule ex- cept general facts. True enough in itself, ne\-ertheless the cross-examin- ing lawyer can make such evidence almost worthless.




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��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 "obser\ation, knowledge and deduc- tion." If the car in ciuestion has a crown mudguard, for instance, one glimpse of a flat or oval mudguard is sufficient in- formation. 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 out- let men to know the various makes is obvious. Even- tually every man on the force will receive some in- struction along these lines, and a short course has already been in- corporated into the schedule of train- ing for recruits.

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���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 auto- mobile is a good index to its lineage

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