NEW YORK -- Television teaches us many things, but nothing more than perseverance.

You know, perseverance, from the Latin for get good ratings so you stay on the air. And what better examples of perseverance could we look to than Fox's 24 and NBC's Law & Order?

Law & Order, duh. After premiering Sept. 13, 1990, it hung on its first few seasons, despite so-so ratings. Then it caught fire. Now a Top 10 show with a guaranteed pickup through 2004-05, it will overtake Dallas and several others, surpassed only by the 20-year marathon of Gunsmoke as the longest-running fiction prime-time series in TV history.

It has also spun off two companion hits for NBC, Law & Order: Special Victims Unit (now completing its fourth season) and Law & Order: Criminal Intent (its second).

Tomorrow at 10 p.m. Law & Order airs its 300th episode (and 13th season finale). But that's not all. At 9 p.m., catch another new episode and, at 8 p.m., the Law & Order pilot (titled Everybody's Favorite Bagman), first seen Oct. 30, 1990.

The cast for the pilot -- Chris Noth, George Dzundza, Dann Florek, Michael Moriarty and Richard Brooks -- has turned over several times in a process of renewal that has led to current stars Jerry Orbach, Jesse L. Martin, S. Epatha Merkerson, Sam Waterston, Elisabeth Rohm and Fred Thompson. Thus, Law & Order reminds us: Stand fast with constant change (which also holds down talent costs).

And what of 24? This serial thriller is no ratings champ. But in best never-say-die style, it got an unexpected reprieve after its freshman season, snagged a bigger audience this year and has won renewal for a third.

Meanwhile, it dwells like no other show on indefatigability -- especially as displayed by Jack Bauer, a former CIA agent who must save the world in 24 hours without so much as a bathroom break.

With the airing of the 24 season finale tonight at 9 p.m., we will learn if he pulls it off.

This season's ordeal and Bauer's longest day ever (at least, since last season, when, during 24 hours, he rescued David Palmer, shoo-in candidate for president, from an assassination plot) began at 8:24 a.m. Bauer was summoned by President Palmer to keep a terrorist-planted nuclear device from leveling Los Angeles.

That episode and the 22 that came after tracked in real time, hour by hour, a multi-strand narrative of action and intrigue with Bauer (Kiefer Sutherland) smack at its centre.

Talk about perseverance! Not only must Bauer do a lot of strategizing, speeding through L.A. traffic and futzing with his cell phone, he has even bigger headaches. Just a sample from his hectic day: He had a wooden stake driven into his thigh during a plane crash, parachuted from another plane within sight of a nuclear eruption, suffered electric-shock torture, died, was brought back to life, withstood more torture and managed to escape.

In short, our hero Bauer is a human Wile E. Coyote, a glutton for punishment who can take falls or get blown up and snap back, good as new, by the next scene.

Granted, the Coyote is doomed to failure in his mission to catch the Road Runner. Will Bauer likewise meet with doom in his ordeal's final hour (on the 24 clock, 7 to 8 a.m.)? Or, once again, will he save the day -- and the world?

On a Law & Order episode, the stakes aren't quite so high.

Typically, someone in New York is found murdered. After many false leads and dead ends, the detectives make an arrest. The lawyers haul the accused into court in a case that often takes expected twists.

To be more specific: On the 300th episode, Smoke, the infant son of a famed comedian, dies after being dropped from a high-rise window, whereupon Detectives Briscoe and Green (Orbach and Martin) uncover the comic's dark secret. But can the prosecutors get that damning evidence in front of the jury?

IF YOU WATCH

What: Season finales of Law & Order and 24

When, where: 24 airs tonight at 9 p.m. on CH and Fox; Law & Order airs tomorrow at 10 p.m. on NBC and CTV; NBC is also airing Law and Order's pilot episode and another new episode tomorrow, beginning at 8 p.m.