THE UNICORN of innocence, the white knight's prancing charger and the nags of the Apocalypse share a pedigree that's magical. Horseshoes bring us luck. Nightmares brings us terror. Each boy who dreams of riding the winner of the Triple Crown, Bucephalus or Silver, each girl who falls in love with Flicka or Black Beauty, reenacts an ancient mystery. In the long and inexplicable history of art there are few recurring icons so sensuous, so potent, so rich in implication as that of the horse.

We were in thrall to his beauty long before we tamed him. Some 32,000 years ago, near the place that's known today as Vogelherd, in Germany, an artist carved -- of mammoth tusk -- a little horse as lovely as those that ride the Parthenon. The Chinese modeled horses, as did the Egyptians. Leonardo painted them; do did Eakins and Degas, Delacroix and Durer, George Stubbs, Franz Marc, Picasso and a thousand other artists. Though cars have long replaced them, horses move us still.

Horses made of wood ride around our merry-go-rounds and, rocking, charm our children. Galloping through surf, stallions suggestive as Godiva's sell perfume on the tube. Little horses made of chrome decorate the hoods of cars. Large ones of cast bronze bear the metal heroes who stand guard in our parks. A centaur, learned Cheiron, reared Jason and Achilles. Businessmen wear cowboy boots, the president wears riding clothes. To make a man a hero is to place him on a horse.

Horses may ennoble, but they also summon terror. In myth they're partly monstrous. The skeleton of death rides a pale horse. Horses scream in Guernica. Hercules did battle with flesh-devouring mares. Pegasus, the flying horse, was born out of the corpse of snake-headed Medusa and, later, threw Bellerophon, who wandered ever after "lame, blind, lonely and accursed."

Horses of the heavens pull the chariot of the sun. The horses of the underworld took Persephone to Hades. The sea has horses, too.

There are images in art -- the thorny rose is one, the sailing moon another, flowing drapery is a third -- that, with eerie constancy, recur in every age. Part sacred, part scary, they carry layered meanings the mind cannot decipher. pAmong the oldest of these icons is the figure of the horse.

It tends to reappear where one least expects it. It reared up here last week, wreathed in glistenings and rainbows, in the art of Washington's Rockne Krebs.

Krebs is widely known for the abstract floating structures he has built of sun an laser light. But his new sculpture depends less on marvels of technology than it does on metaphor. His art is now on view at the Midendorf/Lane Gallery, 2009 Columbia Road NW. Krebs' exhibition there is called "The Spectral Horse."

Man of War, Citation, the Godolphin Arbian -- for most of human history the velocity of horses seemed a limit as unbreachable as the speed of light: He who rode on horseback went as fast as man could go. Misty, Velvet, Trigger, Traveller, the Trojan Horse, the hobby-horse, the Flying Horse of Kansu. Our lore is full of horses. Champion, the Black Stallion, chargers, palfries, Morgans, pintos, mustangs, Clydesdales, Caligula raised his horse to high office; Clever Hans could count.

My kingdom for a horse!"

The horses made by Rockne Krebs of glass and plastic prisms are fastened to our memories. One, his "Special Colt," recalls the toys of childhood. It is a little rocking horse whose build-in wind-up music box plays "Home on the Range." His transparent "Pegasus" is suspended in the air, so that the viewer who moves past it sees all the colors of the spectrum flashing in its hooves, its limbs and its high crystal head. His third piece is a black horse, a partially opaque rearing horse of night.

Krebs' art not so long ago seemed minimalist in spirit. The spectra that his prisms cast, and the glowing lines of laser light he floated over city streets, seemed in many ways less referential than abstract. But Krebs, in the past few years, has opened up his art to old and haunting images, to flowers and to staring eyes, to constellations, pyramids, tornadoes, fans and altars. The horse is not the only old and complex symbol that has surfaced in his art.

His sculpture has never been completely self-sufficient. Krebs, for many years, has worked with time and landscape. It takes a year to see it, but the always-moving spectra of his prism pieces map the cycle of the seasons. bThose startled by his laser beams often overlook the way those slender lines of light bring clarifying order to the messy twinkle of the urban night. The laser beams he placed above the Mall last summer drew on the Washington Monument a floating eye much like the one that hovers on the dollar bill. The prism piece that he's installed in the Botanical Gardens at the foot of Capitol Hill is an act of homage to the jungle pictures of Henri Rousseau. The images, the metaphos, the literary references long concealed in his art have now become explicit.

Krebs cannot explain why he turned to horses. "The image just crept in," he says. Perhaps, like other artists, he is a sort of medium who summons to his art spirits we all know, and recognize at once, but cannot explain. His new sculptures are in many ways the opposite of slick. He uses glass that has been shattered, and threaded screws that one can see. But their roughness does not matter. Long after one leaves his show, his shining "Spectral Horses" remain harnessed to the mind. His exhibition closes on May 23.