God bless Carol Burnett and all the ships at sea. Coming upon her brand-new, four-week ABC variety show amid the turkey's burial ground of summer television is like finding a lemonade stand plop in the middle of Death Valley. One is less inclined to critique the quality of the product than to fall into a heap of thank-you, thank-you, thank-yous.

"Carol Burnett and Company," at 9 on Channel 13 tonight, opens with excerpts from the last Burnett show for CBS Mar. 19, 1978, a date that will live, if not in infamy, at least in darned unpleasantness. Burnett's farewell to her viewers after 11 years was the most moving, tearful soliloquy on television in about a quarter-century, since Judy Garland sat on the stage of the Palace Theater and sang "Over the Rainbow" in a hobo outfit on "Ford Star Jubilee."

What Burnett's brief return -- embarked on as a lark, she says -- makes painfully clear is not only how much her brand of sketch comedy is missed on television, but how sad it is that prime time is now completely berefit of regular variety hours -- not even groaners like "Donny and Marie," which was almost better than nothing. We are witnessing the second death of vaudeville in our time, and TV is left largely to the canned sitcom and the pat filmed drama.

Even operating at summer speed, Burnett and her ensemble -- including the quixotically gifted Tim Conway, agreeably pudgy Vicki Lawrence, and ripe bananas Kenneth Mars and Craig Richard Nelson -- bring television momentarily to life; however accomplished the script and inspired the clowning, the Burnett show also represents congeniality raised to the status of art. It is an hour we get to spend in the company of deliriously talented friends.

The program includes a reunion for Burnett's terminally daft and bottom-heavy Mrs. Wiggins and Conway's befuddles Mr. Tudball, an amusing interruption by Mars as a man with his chin in a sling, and a series of blackouts on the subject of "Palimony." In one of these, Burnett, as a gap-toothed old crone on a park bench achieves the nearly impossible by breaking up Conway as she rattles on aimlessly with a tale of a squished associate.

And in the best tradition of TV variety, Burnett duets such guest star Cheryl Ladd (can't sing, can't dance, can't miss) with slightly revised lyrics to the pop tune "Just the Way You Are." At one point Ladd sings, "Carol, I love you, and that's forever." At another point Burnett gives the glamoroso Ladd the definitive rendition of the envious once-over. Ladd is wearing this clingy, long blue tube thing and she looks good enough to make a million dollars weep.

Burnett explains at the show's opening how she hopes the limited-run summer series will become a tradition, a "class reunion" for the old gang. "If it works, we want to do it every August, she says, which is the only thing to be said in August's favor in years. She doesn't mention that former co-star Harvey Korman unwisely declined an invitation to return (preferring, apparently, to waste his time on lame movie comedies like the current "Americathon") or that in a fit of feckless ingratitude, CBS declined the option to carry this summer series, even though it is Burnett's home network and the program is taped at CBS Television City in Los Angeles.

"Welcome to our little summer show," Burnett says unpretentiously near the opening. "I couldn't stay away." Her decision to come back even for four weeks ranks as a virtually humanitarian gesture and provides a refresher course in what entertainment is supposed to be. For those who didn't realize what great fans they were until Burnett tugged her ear goodbye that dark night in '78, of course, the program also constitutes a generous reprieve, an opportunity to say, no bones about it, "Carol, I love you, and that's forever."