_Bull-traps_.--Rogues who personate officials to extort money. We could multiply these examples, but the above are sufficient to illustrate this branch of our subject. PROFESSIONAL THIEVES. The poor wretches who steal a few dollars' worth in open day, from stores and stands, are not considered by professional thieves as amongst the "fraternity," which embraces house-breakers, pick-pockets, and burglars. These persons are carefully trained by "old hands," and are by practice made as perfect as possible in their arts. Indeed, to be an accomplished burglar requires a very great degree of intelligence, courage, strength, and ingenuity. These men all have certain distinct methods of performing their work, so that after they have been operating a short while, a detective can, by examining the traces, tell, with absolute certainty, the name of the burglar. Besides this, the life which these persons lead stamps their countenances and general bearing with marks which an experienced officer will recognize at a glance. The sneak-thief, the pickpocket, and the burglar, have certain habits, attitudes, haunts; they act in certain ways when placed in certain positions, which reveal them and their occupations to a practiced eye, with almost as much certainty as the form and aspect of a blade of grass reveals its genus and species to the eye of a practiced botanist. A skilled detective will stand at the corner of a street, in a strange city, that he has never entered before, and will pick out, almost unerringly, the passers-by who belong to this criminal class. He will say, "This is a sneak-thief;" "This is a pickpocket;" "This man has just been released from the State prison;" "This one is a gambler, stool-pigeon," etc., etc.; being guided in his judgments by certain indications which the criminal involuntarily displays by the sheer force of habit. A sneak-thief will pass along with that rapid, rolling glance of the eyes which distinguishes the tribe; now he checks himself in his career; it is but for an instant; no unprofessional eye directed towards him would notice it; but the sudden pause would speak volumes to an experienced police officer. He knows that the thief's eye has caught the sight of silver lying exposed in the basement. In an hour after he hears that the basement has been entered, and the silver in it carried off. He knows who has taken it, as well as if he had seen the man take it with his own eyes; but if the thief has had time to run to the nearest receiver's den, the silver is already in the melting-pot, beyond the reach of identification. HOW FINE HOUSES ARE ROBBED.