It is a pity that a performance like Emlyn Williams doing Charles Dickens couldn't be bottled somehow, and taken out regularly like a good brandy, for drinks at appropriate occasions. Taping for television -- which has been done -- is not quite the answer, with its enforced unreality and inevitable distance from the immediacy of what is increasingly, and regrettably, called "live theater" (as opposed to dead television, presumably).

Williams has been doing Dickens on and off for 30 years now, including a previous visit here in 1975, and his performance has attained a patina reminiscent of aged, well-polished wood. He'll be doing the one-man show at the Terrace Theater through Sunday, an opportunity for anyone who likes Dickens to appreciate him anew, and for those who don't to have another chance.

The menu is much the same as it was in 1975, a sampler of the gory as well as the literary Dickens. There is the wonderfully catty Dickens of "Our Mutual Friend," describing some arrivistes as being so new that "if they had . . . a grandfather he would have arrived in a packing case," and the dinner table with "the big silver spoons wide in the mouths of the company."

He is the pathetic dying child in "Dombey and Son," and the dwarf Mr. Chops from "The Tale of a Little Person." Williams originated his show in imitation of the writer, who toured around giving, in effect, concert versions of his work. It is likely that Williams is better at it than Dickens was.

His virtuosity is characterized by a kind of a control, a control that is only partly due to the fact that, after all these years, he knows the words without the slightest hesitation. His control also includes a playful freedom with the words. When he says a lady looks "like a face in a tablespoon," he makes a face to illustrate; he uses sharp intakes of breath carefully orchestrated to conjure a hanging, weeping, or to punctuate.

When he jumps up and down as the dwarf or as a bouncing carriage, it is only slightly rude to remember that he is 76 years old; the only sign of this alleged age is his white hair. He glides from one character to another almost in mid-word, changing his voice, an eyebrow, a posture.

Not all the excerpts are equally successful. A description of a battlefield -- which he calls "a landscape" -- from "The Battle of Life" seems melodramatic, and the suspense of "A Call Upon a Strange Man" is contrived. But for all those who would purge the saccharin accumulated from too many "Christmas Carols," or who wish to sample a bit of the genius that inspired "Nicholas Nickleby," this is the show to see.