Midway through the Lawless Decade and having a wondeful time, Baghdad-on-the-Subway ousted the stuffy John F. Hylan and got itself the right Mayor for the right moment.   James J. Walker, called Jimmy, eased his trim frame behind the big colonial desk in City Hall on the first day of 1926 and looked impishly around the musty, high-ceilinged room; he would not spend too many of the precious hours in those dim-lit, austere precincts.

So Jimmy Walker turned on his puckish Irish grin, called for his walking stick and his gray spats and silk topper and went uptown where the lights were brighter.   He went up to Broadway, where he was at home.   The town came to know him as the high priest of live-and-let-live--in all the departments, including the increasingly less sacred institution of marriage.   The Man-About-Town stopping at the Central Park Casino for a nightcap with his best girl, not to be confused with his lawful wedded wife, could take comfort that the Night Mayor was also on the premise--with his best girl.

The vast Walker fame did not derive solely from his lively taste in the fair sex, of course.   He came into City Hall with a solid 14-year record in the State Legislature behind him.   He wrote the bills that legalized boxing in New York and let the theaters stay open on Sundays.   Cast in the liberal image of his political sponsors, Gov. Al Smith and Senator Robert F. Wagner, he fought for the 5-cent fare, for the eight-hour day for working women, for workmen's compensation laws, for tenement safeguards.   Quick on the tongue, he killed a move to censor novels with one swift wisecrack:   "I have never yet heard of�a girl being ruined by a book."   Between times Tammany's dandy little lawmaker managed to string together the lyrics of a ditty that, like some of his municipal deeds, would live after him--"Will You Love Me in December as You Did in May?"

Always a familiar figure around Tin Pan Alley and the adjoining hot spots, Walker unfailingly selected his female partners from behind the footlights.   He picked pretty little Janet Allen out of a chorus line in 1912 and made her his wife, only to stray after a while when songstress Yvonne Shelton came into view.   Miss Shelton--"Vonnie" or "Little Fellow" to her favorite swain--had to be sacrificed in 1925.   Al Smith was afraid that the open dalliance might cost Walker the election, so the candidate dutifully went back to his wife.   The political patch only held the union together for a year, or until the Mayor's bedroom eyes alit on beautiful Betty Compton, playing a small role on Broadway in Gertrude Lawrence's starring vehicle, Oh, Kay!   This May-December romance--the actress was just half the eternally boyish Mayor's 46 years--was the big one for Walker.

The 1929 campaign, coming after four more years of bad booze, hot jazz and wonderful nonsense in the Big Town, effectively laid to rest Mr. Smith's early fears about the effects of open amours on the voting populace.   The Night Mayor, also known as the Late Mayor because he seldom got to City Hall before high noon and almost never kept an appointment on time, ran for re-election against the popular Fiorello H. LaGuardia and won by half a million votes.   Everybody loved the smiling Irishman from Greenwich Village.   Nobody expected him to work his fingers to the bone in that municipal factory downtown; he belonged to the Great White Way, or maybe on Fifth, marching up the golden avenue in the van of some parade or other.

And then along came Samuel Seabury, the good, gray, solid rock of respectability, poking around in the dungeons of the gay and prospering metropolis . . . rattling the skeletons . . . tracking down the vice cop's ill-gotten gains to find out why the town was wide-open for the streetwalker legions . . . turning the bus franchises and the sewer contracts and the stock deals over to a platoon of investigators and accountants . . . making magistrates squirm as they tried to explain why they were always so kind to policy runners and other politically-favored defendants . . . asking razor-edged questions . . . digging deeper and deeper and ever deeper.

Not all the murky trails led to the man in City Hall--not by any means--but the tireless Judge Seabury and his bright young helpers did turn up some embarrassing items directly involving Jimmy Walker.   "Little Boy Blue is going to blow his horn--or his top," said the brash and dapper $40,000-a-year Mayor on the way into the hearing room.   But he came out tarnished.   He couldn't explain--at least not with any conviction--how he happened to make $26,535.51 in oil stock deals with taxicab impresario J.A. Sisto without having to invest a dime of his own.   Nor why J. Allan Smith, contact man for a bus company, staked him to a European jaunt in 1927 with a $10,000 letter�of credit and an extra $3,000 to cover an overdraft.   Nor how he happened to pick up a $246,000 bonanza in a joint stock account with Paul Block, Brooklyn financier and publisher.   Block's own story didn't help; he said that his 10-year-old son once observed that the world's richest city didn't pay its Mayor enough, so he decided "to make some money for Jimmy."

The mounting Seabury revelations prompted Governor Franklin D. Roosevelt to set up hearings to determine whether Walker should be removed from office, but the Mayor didn't wait for the ax to fall.   On Sept. 1, 1932, he resigned and fled to the Continent.   He had Betty Compton by his side, as ever, and soon he was able to make it legal when Janet Walker obliged him, after all those years, and got a Florida divorce.   Walker and Miss Compton were married at Cannes, France, even while the ink was settling on the decree.   The union only lasted until 1941, when Miss Compton got a divorce of her own.

Jimmy Walker never talked for publication about the events that led to his downfall. Asked about the high old days in sinful Manhattan, he said somewhat wistfully that he wished he knew where all the money was that he supposedly had stolen while he was at the helm, but that only made the untold story a little more intriguing; it didn't tell anything.   The plain citizen of New York, for his part, looked with much tolerance on the tainted record.   When Walker came back from exile in 1935, satisfied that he would not be brought to trial, his great popularity hardly seemed dimmed; the welcome mat was out.   In no time at all he was the town's favorite after-dinner speaker and again a familiar figure in public places.

If he had any massive guilts, either about his private or official life, he kept them to himself.   In the days when the storm clouds were thickest, he went before a huge banquet audience and put his case this way:

"I have lived and I have loved.   The only difference is that I was a little more public about it than most people.   After all, maybe it isn't a mistake to be one's self and take chances.   With all my misgivings, my countless mistakes, with all my multiplicity of shortcomings, I have a single regret.   I have reached the peak of the hill and must start the journey downward.   I have carried youth right up to the 5O-yard mark.   I had mine and made the most of it."

Maybe Gene Fowler, his biographer, said it even better than the eloquent Walker, He said Jimmy "wore New York in his lapel like a boutonniere."   In those days, mixing a Prohibition that didn't work with a who-gives-a-damn prosperity that didn't last, a man could do that.