Alan Bates staggers through the crowd, his eyes rolling and his mouth forming the sly, secret grin of the drunk who thinks he is playing a joke on the whole world.

"I'll sell 'er for five guineas," he says in the accent of a farm worker from the west of England. "Five guineas . . . to any man 'ere who'll put the money in my 'and 'ere and now . . ."

In one of the most shocking scenes of Victorian literature (which has more than its share), Michael Henchard, unemployed hay-trusser, is auctioning off his wife and infant daughter to the highest bidder.

It is the climactic point in the powerful first installment of Thomas Hardy's. "The Mayor of Casterbridge," which will beaired in an excellent television adaption on "Masterpiece Theatre" tomorrow night (Channel 26 at 9). And it is also the beginning of the spectacular rise and fall of one of Hardy's most complex and interesting targic figures: a weak man who reaches wealth and power but is destroyed by his frantic efforts to be - or at least to appear - strong.

In the first episode, a British sailor who happens to be passing through the fair hears Henchard's attack on his wife: "This woman 'ere ain't no good to me; now, who'll 'ave 'er?" He puts down the required 5 pounds and 5 shillings and goes off with the woman and child. Henchard falls into a drunken sleep, when he wakes up, he begins to fulfill his boast: "If I were a free man again, I'd be worth one thousand pounds."

Before the first installment has ended, 18 years have dissolved, Henchard has become a grain merchant, the richest man in Casterbridge and the town's mayor. The long-lost wife, having lost her sailor-purchaser at sea comes back to look for husband No. 1 and is amazed and somewhat shamefaced at the sight of his good fortune. Perhaps he was right, 18 years earlier, when he put her up for sale, muttering "Women can bring a man down . . . ain't no doubt about that."

The remaining six episodes, if they follow Hardy's novel as faithfully as the first, will be devoted to demonstrating that, in Henchard's case at least, a man brings himself down.

"Character is Fate," says Hardy, admitting in the same sentence that he was not the first to say it - but he illustrates it in this story with a satisfying fullness that soon makes the audience forget the the sometimes creaky elaborations of the plot. Michael Henchard is a rough man, strong-willed and capricious; in the wife-vending episode, he can blame it on rum, but 18 years later, after successfully swearing off alcohol, he is much the same except that he doesn't stagger.

In a sense Hardy is an easy writer to adapt for television; his main attraction lies not in an exquisite prose style or in subtle symbolism and intricate development of themes (all of which tend to get diluted in translation to the screen), but in the simple stark power of the story itself and the characters it involves.

Some of his scenes even gain in the transition. The slightly arid prose comes to life when it is translated into glowing pictures of the green English countryside or the bustle of a marketplace, a country fair. And the dialogue which tends to lie flat on the page sometimes becomes warm and vivid in the mouths of good actors.

In Henschard's final downfall each of the people he has wronged will play a role: the wife he scorned publicly, a business assistant whom he forced to become a rival, a mistress whom he promised - then refused - to marry.

But his worst enemy is his own knack for turning people and things against himself. He loses for example, in a wild, make-it-or-break-it speculation in grain futures, and he can blame the weather for his loss but only Michael Henchard is to blame for being in a situation where he needs the right kind of weather to survive.

Among the actors, Alan Bates is easily the most notable, taking a role that is long and not easy to make believable and giving it the proper larger-than-life reality.He is well supported by the women who "bring him down": Anna Massey with just the right blend of caprice, iron determination and vulnerability as the scorned (and later scornfull) mistress, who will not appear in the first episode; Anne Stallybrass as the weary and put-upon wife; Janet Maw, still young and relatively inexperienced but sensitive in her portrayal of the daughter.

Jack Galloway, in a strong supporting role, rounds out a distinguished cast, but the high-quality acting in this production is not limited to the stars; in the auction scene, there are several walk-on roles with a few sentences, each characterized with an individuality that borders on eccentricity, and a polish that one does not find among the biggest names in the current crop of American actors.

Director David Giles is becoming something of a specialist in this period, with "The Forsyte Saga," "Sense and Sensibility" and "Vanity Fair" among his previous television credits. The smooth flow and precise attention to authentic flavor and small details in this production will certainly enhance his reputation.

Writer Dennis Potter, adapting the novel for the screen, has taken the kind of liberties one expects in such an adaptation. The story is somewhat simplified, with whole scenes and a few characters omitted. Part of the reason for this is that a drama has to move faster and more simply than a novel, but some of it is economic. It costs a - novelist only a few strokes of the pen to have two hotels rather than one in the first episode; it would cost a television producer a lot more.

Those who already love Hardy will naturally miss some of the things that make his novels distinctive - the little essays about relics of the Roman Empire in Casterbridge, for example - but there is no way to save them for television. The important point is that this dramatization shows a proper respect for the novelist's material and methods and purposes.

To do justice to "The Mayor of Casterbridge," seven hour-long installments are needed. Public Television (or its BBC source) deserves credit for seeing and fulfilling that need.