BUCKMINSTER Fuller is one of the more fascinating, multifaceted beings to inhabit the planet--architect, engineer, mathematician, cartographer, writer, philosopher, teacher. He also is an inspired inventor, the quintessential Yankee tinkerer, and it is in this guise, mainly, that he appears at the Fendrick Gallery in an exhibition continuing through Saturday.

As a boy growing up on a small island in Penobscot Bay, Maine, Fuller would row each day on a four-mile round trip to get mail. His first "teleologic design invention," he once wrote, came from that experience. It was a "mechanical 'jellyfish,' or teepee-like, folding, web-and-sprit cone mounted like an inside-out umbrella on the submerged end of a pole." With the aid of this device, Fuller recalled, he was able "to push-pole the boat along far more swiftly and easily than by sculling or rowing."

Fuller has never forgotten his nautical roots. In his writings he repeatedly uses the complexity of forces affecting watercraft design as an example of synergetic efficiency at its best. And he still designs boats. The Fendrick show, for instance, contains his patented 1968 design for a rowing needle--"a catamaran with twin hulls surmounted by a sliding seat and affording minimal water resistance."

There is something of this wondrously simple, or simple-seeming, ingenuity even in Fuller's more complex inventions for houses, domes, space frames, automobiles and whole cities, something at once playful and serious, marvelous and efficient, surprising and obvious. The current exhibition is a condensed retrospective of Fuller's inventions--13 of them, dating from 1927 to the 1970s, each with a screenprint of illustrating a drawing for a patented invention and a screenprint image of a photograph illustrating the final product.

The show tells a beautiful story of supreme intelligence and boundless optimism, and yet it also contains a paradoxical undertone of frustration. Although Fuller's geodesic domes are known and used worldwide, many of his inventions were produced in disappointingly small quantities. Each of his Dymaxion houses (dymaxion is a word he adopted, meaning "maximum results with minimum input of materials and energy"), for instance, were seriously intended as prototypes for mass-produced housing to solve worldwide needs, but none ever reached a production line.

Fuller obviously recognizes this rejection--he has written of the "vast dollar-powerful lobbies concerned primarily with permanentizing all the inefficiencies of Class Two environment-controlling arts"--but he remains undaunted and amazingly unembittered by it. He continues on his unique way. As Calvin Tomkins writes in a prologue to the current exhibition, "Bucky often tells his lecture audiences that he is the most ordinary person he knows. Anybody, he says, could have done what he has done . . . That may be so, but nobody else has done what he has done, or anything like it."

The Fendrick exhibition encapsulates an important piece of 20th-century intelligence and ingenuity. The prints are for sale at $900 each or $9,000 for the whole series. Anyone lacking that kind of money or interest can still take away a provocative memento: a punch-out Dymaxion map of the world, on sale for $5. The gallery is located at 3059 M St. NW. Hours are 9:30 a.m. to 5:30 p.m. Through Saturday. Trevor Bell's Light Tricks

Trevor Bell, an English artist who has been working for a decade at Florida State University in Tallahassee, is a believer in the transformative magic of color, and he is not above using a trick or two to achieve his ends. For example, in "Light Trap," an impressive, huge diptych in his exhibition at the National Academy of Sciences, Bell employs a vibrant lemon yellow on the hidden beveled edge between the painting's two parts. Combined with sharply angled lighting from above, this device produces an intense, preternatural glow on the wall to enliven a composition already distinguished by searing juxtapositions of colors.

"Light Trap" is perhaps the best painting in the show. Composed of two horizontal, truncated pyramid shapes, it embodies Bell's intention to work on an architectonic scale in elementary, "primitive" shapes. Each of Bell's paintings contains superb, intense passages of color, but there also is a seeming tentativeness, a lack of structural precision in the laying on of colors, that often disrupts the intended grandness of effect. Through May at 2101 Constitution Ave. NW, open from 9 a.m. to 5 p.m. Mondays through Fridays.