The most shocking thing about "The Shock of the New," the eight-part TV series which begins tomorrow night at 8 on Channel 26 is that it's there at all. For "Shock" is about art, and TV's coverage of painting, with one notable exception, always has been zilch. The exception is, of course, the work of Kenneth Clark.

A dozen years from now, when "Shock" is standard fare in colleges and high schools, it no doubt will be dubbed "Son of Civilization." But though the new series begins where the older one left off, no one would confuse Robert Hughes, its host, with a son of Clark's.

Clark used to be Sir Kenneth and is now Lord Clark of Saltwood. He is urbane, aristocratic, scholarly and tweedy -- one might almost say antique. Hughes isn't. A former painter, former draftsman, former TV failure, he is, at 42, less polite than pugnacious. Connoisseurs of painting are frequently supposed to be men of utmost delicacy. Hughes, who writes for Time and whose voice is a deep bass, instead calls to mind an Australian toughie who's begun to go to seed. He is probably the best mass-media art critic alive.

He tried TV before. He once worked for Roone Arledge as a host on "20-20." "They offered me the mountaintop, pots of money, fame and the love of women, so, of course, I signed." Last time around he blew it. "My motto," says Bob Hughes, "is once bitten, twice bitten." "Shock" may make of Hughes an authentic TV star.

"Shock" is thoughtful stuff, half as glitzy, twice as solid as the Star Bores of Carl Sagan. It does employ some TV tricks. Hughes will start a sentence in Manhattan, continue it in London, finish it in Paris, but such hops have a purpose. It is the swift crosscutting, both visual and mental, that gives Hughes' work its density. His programs offer more than images of art works. He shows us splendid film clips of Edison and Duchamp, of Albert Speer and Einstein, of Lenin, Mussolini, and the sodden, stinking trenches of the Somme. His programs tell us quite as much about our era's history as they do about its art.

"Television is useless for conveying abstract argument," Hughes says, "it can only show and tell." But he does more than that. Ideas and information fly off the facts that he conjoins, and off the gaps between them. What he shows us is worth seeing, and what he tells us should be heard. t

In "The Powers That Be," the second program in the series, which deals with the art of authoritarian governments, he shows us how the art of the Russian Revolution uncannily resembles that of the early reign of Benito Mussolini -- and how the later public architecture of Il Duce's fascist Rome is as closely tied to that of our own day.

Hughes suddenly is standing on the reviewing stand at Nuremberg, designed by Albert Speer for Hitler. A few seconds later, we see Hughes in Rome at Mussolini's Forum. "Classicism with a pastry cutter" is how Hughes describes it."Twenty-five years later a lot of southern California universities were going to look like this," and, indeed, they do. So does Lincoln Center (which Hughes describes as "the architectural equivalent of the world's 100 greatest books bound in hand-tooled Naugahyde"), and so does the Kennedy Center, whose blank walls we see next. From Washington we cut to Nelson Rockfeller's Albany Mall, "the scariest monument I know. It makes Albert Speer seem delicate. Any one of those buildings you can imagine with an eagle on the top, or a swastica, or a hammer and cycle -- it makes no difference."

"As far as today's politics is concerned," says Hughes, "art aspires to the condition of Muzak. It provides the background hum to power. If the Third Reich had lasted until today, the young bloods of the party would be lining up to have their portraits done by Andy Warhol." By now one believes him. That point was worth the trip.

Hughes, still an Australian citizen, was born in Sydney, "that great Pacific port of which San Francisco is a meager imitation. My people were Irish bogtrotters. The first Hughes out there was a superintendent of convicts in the 1830s. In those days there were but two classes of Australians -- the jailers and the jailed. My grandfather eventually grew inordinately rich, but then, alas, was overcome by the old religion and gave his cash, and a mile of Sydney's foreshore, to the sisters of the Church.

"My grandfather was the first Lord Mayor of Sydney.His son, my father, was a pilot in World War I. The first painting I can remember showed him in a biplane dueling with von Richtofen. They both missed. I went to this tremendously authoritarian Jesuit school. As soon as I got to university -- Germaine Greer was a classmate -- I discovered girls and booze and atheists, and failed, failed utterly. I was trying to be an architect. I was doing renderings of the Parthenon in 143 washes of Chinese ink, and drawing cartoons on the side for the Sydney papers of the young Rupert Murdoch. It was about that time I started writing about art.

"I was painting, too -- Antipodean de Koonings. The last place in the world where there was a real battle between the Abs and the Figs was in Australia. They threw bottles at each other. It was the real Wild West. Once I panned a Fig, Dickerson by name, and he responded bluntly. He knocked me cold."

Australians, in those days, used to suffer dreadfully from what Hughes calls "cultural cringe." So in 1964, he set out for Europe, first to England, then to Italy. In the last years of the '60s, he published a book on "Heaven and Hell in Western Art," "now a volume of extraordinary rarity." His book was somehow read by an editor at Time. The magazine in those days had just begun to offer bylines to its critics. Hughes, in 1970, was offered the Time job.

Hughes is now writing a book on the prisoners of Australia. "I'm going to call it 'Chains.' He also is planning a television series on American art. "For cable," he insists. "I'll never work again for commercial television. My experience at '20-20' would make the movie 'Network' seem a harmless skit." "The Shock of the New," like "Civilization," was produced by the BBC.

"Kenneth Clark," he says, "was one of my first models. He wrote the sort of prose I wanted to write -- unfussy and uncondescending. Later he'd become the father of popular cultural television. I never bought that stuff about Clark being a vulgarizer. There is no Oedipal passion here. Clark is a genuine natural popularizer."

So is Robert Hughes.