ABOUT an hour into ''Harry Potter and the Chamber of Secrets,'' Harry (more often referred to as Mr. Potter or the Famous Harry Potter) discovers, much to his amazement, that he can speak the slithery, sibilant language of snakes, which is called Parseltongue. For the audience, a similar shock arrives much earlier, the very first time Daniel Radcliffe, the young English actor who plays everybody's favorite English schoolboy wizard, opens his mouth. Though Mr. Radcliffe remains smooth-faced and wide-eyed, his voice (like that of Rupert Grint, who plays Harry's pal Ron Weasley, and Tom Felton, as the odious Draco Malfoy), has begun to break, and he speaks in the unmistakable, awkward tongue of adolescence.
But ''Harry Potter and the Onset of Puberty'' may have to wait for the next installment, when Alfonso Cuarón takes over the franchise from Chris Columbus, who directed this episode and its predecessor, ''Harry Potter and the Sorcerer's Stone.'' Mr. Cuarón, whose most recent film was the moving and irrepressible teenage sex comedy ''Y Tu Mamá También,'' may be the perfect man for the job, though parents worried about an unrated, sexually explicit ''Harry Potter and the Prisoner of Azkaban'' should remember that Mr. Cuarón also directed a superb adaptation of ''The Little Princess.''
In any case, Mr. Columbus, once again working with the screenwriter Steve Kloves and a cast of talented children (especially Emma Watson, who plays the brainy and intrepid Hermione) and grown-up British luminaries, has acquitted himself honorably. ''Sorcerer's Stone,'' while far from a great movie, was good enough. Mr. Columbus (who is also an executive producer of the films) has faced the unenviable and unusual challenge of adapting books most of the audience will have read closely and recently. And a very demanding audience it is. My fellow critics and I may occasionally fault a movie for departing, in detail or in spirit, from its literary source, but the grousing of a few adult pedants is nothing compared to the wrath of several million bookish 10-year-olds.
Their presumed demands, and the hovering spirit of Harry's creator, J. K. Rowling, inhibit this movie as it did the first Potter film. Near the end of this one, Albus Dumbledore (Richard Harris, in his last screen performance) sternly notes that Harry and Ron have broken at least a dozen rules in the code book of their school, Hogwarts, and then gives them a special award for service to the institution. Until the filmmakers absorb this lesson and show themselves willing to risk getting into trouble, no special awards are likely to be forthcoming for them. But passing grades will at least earn them their allowances. Because it is based on a richer, more interesting book -- so far Ms. Rowling's novelistic skills have grown, along with her ambitions, with each successive volume -- and partly because the director shows more dexterity and imagination of his own, ''Chamber of Secrets,'' which opens nationwide today, is a little better than ''Sorcerer's Stone.''
And at 2 hours 41 minutes, quite a bit longer. Ms. Rowling has been loudly praised for sparking the younger generation's renewed interest in reading, and Mr. Columbus may soon be credited with curing its notoriously short attention span. At this rate ''Harry Potter and the Goblet of Fire,'' the 752-page fourth volume, is likely to spawn the highest-grossing seven-hour film epic in history. (Too bad Erich von Stroheim isn't around to direct it.)
But for now the length is less of a problem than the pacing. Much of the fun in the books comes from how swiftly they move, and how much detail and information they carry along in their eddying, tumbling narrative currents. Ms. Rowling is capable of remarkable shifts in tone, gliding from comic observations of daily life at Hogwarts to tremors of absolute evil with a sure, deft touch.
Mr. Columbus, in contrast, is a master of the obvious and the emphatic. After the boisterous clowning of the opening set piece -- which involves the ritual humiliation of the Dursleys, Harry's swinish Muggle guardians -- the picture settles down into a plodding, heavy rhythm. Don't get me wrong: many of the sequences are thrilling. The digital editing of the high-flying Quidditch match is notably improved, and the monstrous special effects, including an angry tree, a swarm of spiders and a giant, slimy basilisk, are vividly creepy.
There is also an anarchic, rubbery computer-animated elf named Dobby, who steals every scene he appears in from the more restrained flesh-and-blood cast members; a shrill ghost named Moaning Myrtle (Shirley Henderson); and a very scary haunted diary. The visual environment is beautifully conceived and skillfully rendered by Stuart Craig, the production designer, and Roger Pratt, the director of photography: more than in ''Sorcerer's Stone,'' Hogwarts has begun to seem like a real place.
But the movie's scenes feel cut to uniform length and arranged in plodding, unvarying rhythm. Every speech and incident is blown up into a big effect, and as a result the quieter, quirkier aspects of Ms. Rowling's world are pushed to the edge of the frame, or left out altogether. The sense of a dramatic crescendo is lost, so that by the end, instead of feeling stirred to a high pitch of anxiety and excitement, you may feel battered and worn down.
But not, in the end, too terribly disappointed. I did wish that Alan Rickman and Maggie Smith -- who return as the rival housemasters Severus Snape and Minerva McGonagall -- had more to do, but their absences are compensated for by Kenneth Branagh as a self-adoring teacher of defense against the dark arts, and Jason Isaacs as the viperous Lucius Malfoy, father of Draco. Mr. Harris, who died last month, gives us a last taste of his whispery, mischievous wisdom, and Robbie Coltrane, as the doting, bumbling Hagrid, has a welcome Falstaffian vigor.
The story would be hard to ruin. It moves, as always, simultaneously backward and forward, toward the mysteries of unfinished wizard history and through the passages of Harry's coming of age, tripping us up with the subtle differences between ordinary bad behavior and true evil. It does, however, remain more lively, and more at home, on the page.
''Harry Potter and the Chamber of Secrets'' is rated PG (Parental guidance suggested). It has some very frightening scenes, especially for viewers who are afraid of snakes and spiders.
