Each year the Hull Gallery combs the market for high quality American art from the past, and offers it for sale in its pleasant establishment at 3301 New Mexico Ave. NW. Despite dwindling supplies and soaring prices, Hull's current show "American Paintings and Drawings, 1830-1950," is one of its best.

Most of the works are small, one of the smallest being the most important -- a tiny still life with books by trompe l'oeil painter John Frederick Peto (1854-1907) who will be the subject of a major exhibition at the National Gallery of Art in early 1983. Other early examples include the requisite number of Hudson River School and Luminist works -- though of varying quality -- and a fine little Civil War drawing by Winslow Homer of "Soldiers Leaving Alexandria for Fortress Monroe," the price of which will knock your socks off.

But the best of these 70 works are from the early 20th century, and are capped by a moody little 1908 crayon and ink drawing by George Bellows (1882-1925) depicting several women chatting away on a snowy New York street. There are several good examples by early American modernists, notably artist-immigrants like Oscar Bluemner, Abraham Walkowitz, Max Weber (a superb small tempera of a woman in a garden) and Louis Lozowick, whose half cubist, half futurist pencil drawing incorporating the Manhattan skyline is worthy of a museum.

There is more: a charming pastel by Jerome Myers, titled "Women and Children On the Ferry," and an unusual painting of a sunset by a man better known for his illustrations: Rockwell Kent. John Marin's early, Whistler-like watercolor of "Paris, Early Evening" is another of those happy surprises that makes exhibitions of this sort so revealing. The show is open Mondays 1 to 5 p.m.; Tuesdays through Saturdays, 10 a.m. to 5 p.m., through Feb. 27. Few More Mehrings

Fans of the late Washington Color painter, Howard Mehring, are in for a big disappointment. When Mehring died in 1978 at the age of 47 -- two months after his stunning retrospective at the Corcoran -- it was hoped that some subsequent showing of his work might unravel the mystery of his life, and finally shed some light on why he suddenly stopped painting in the '60s.

It was also hoped that his estate would reveal a cache of hitherto unknown works that might at last help establish him in his rightful place among the pantheon of Washington's finest painters.

No such luck. The estate has proved to be thin, indeed, as the paltry show of 10 large paintings at Middendorf/Lane's downtown gallery at 404 Seventh St. attests. A concurrent show at Salander O'Reilly in New York is no better: it consisted of five paintings. Five more were shown recently in Munich.

As it turns out, Mehring left only about 3 dozen paintings behind when he died, most of them hard-edge T and Z forms done in 1966-67, just before he abandoned painting.

There are three examples (though not great ones) from Mehring's best period (1958-59), when he produced billowing, cloud-like paintings made up of stippled color of exquisitely subtle hue. But the emphasis here is upon the later, hard-edge works. There are some strong, richly colored examples, but as a whole, the show leaves one overwhelmingly sad that such a career must end, at least for now, with such a whimper.