YOUNG MAN OF LARGE APPETITE AND SMALL CONSCIENCE.--The necessity of eating is a strong one; the demands of appetite are peculiarly and pertinaciously potent. There are many fleshy-looking young men in New York whose appetital demands are largely ahead of their pecuniary resources, the latter being of a limited nature, like their consciences. Our leading hotel diners are appreciatively affected by these unconscionably-stomached and conscienceless individuals; and it requires all the devices of the proprietors, and ingenious watching of sharp-sighted detectives, to guard against their stealthful appropriation of dinners. In the multiplicity of guests daily arriving at first-class hotels, and multiplied disguises assumed by the unpaying diners, it is easy to conceive that the labor of watchfulness is no light one, and the guarantee of detectives by no means sure. There is no keener man in the Police Department to scent out a rogue than Officer McWatters. He can tell a rascal by a sort of instinct. A stranger to him is like a piece of coin in the hand of the skilful medallist, who tells the spurious from the genuine by the feeling--by a glance even. Officer McWatters measures a man at a glance. He sees the latent roguery peering out of the corner of the eyes, lurking in the smile, hiding itself in the cultivated mustache and careful whiskers, strongly and unconsciously developing even in the gorgeous watch-chain, flashy vest, showy cravat, elaborately-checked pants, and brilliantly shining patents, or, _vice versa_, suit of puritanical plainness. His penetrative optics permeated, yesterday afternoon, the disguise of that most notable and audacious of non-paying hotel diners, Jack Vinton. Jack had taken dinner at the Metropolitan Hotel. His brassy impudence had enabled him to pass muster, as a guest of the hotel, the Cerberus at the dining-room door. Not to betray a dangerous haste in leaving, he sank back leisurely into a soft-cushioned chair in the gentlemen's parlor, and read a newspaper for a while. He was going out of the hall door, when Officer McWatters spotted him. "Are you stopping at this hotel?" asked the officer (who, by the way, was in citizen's dress), in that tone of politeness, for which he is remarkable. "I am, sir." "How long have you been stopping here?" "Ever since I came here." "Is your name registered?" "Registered? I never heard of such a name. Mine begins with an initial letter of higher alphabetical rank." "You misunderstand me. Is your name on the hotel books?" "The bookkeeper is the proper informant." "Have you a suit of rooms here?" "Am suited perfectly--all the rooms I want." "What is the number of your room?" "A No. 1--first-class, sir. First-class hotel has first-class rooms, you see, sir. This is a first-class hotel--the _ergo_ as to the rooms is conclusive." "You are evasive." "Only logical, sir!" "You took dinner just now up stairs?"