AS THE National Gallery's curator of 20th-century art, I have participated in finding A missing modern paintings or making X-ray discoveries of images long hidden under later paint layers. But last summer I found myself engaged in the final steps of a project almost archeological in character--tracking down the physical evidence of the lost plans for a church, a modern one known only by reports so vague as to qualify as rumors. What captured my interest was that this church was supposed to be a collaboration by two of the most important American artists of this century, Tony Smith and Jackson Pollock.

The search actually began almost eight years ago, but it proceeded only piece by piece. I was preparing an acquisition report for the National Gallery's trustees on Pollock's "Lavender Mist," a major abstract picture created in the technique of poured paint that made the artist famous. In studying Pollock's career, I found a puzzling gap. He first began pouring paint in 1946, and continued making these abstract works until 1950, the year of "Lavender Mist." But then in 1951, he suddenly abandoned this style and for no apparent reason. For the next two years he painted stark black figural images on white canvas. Then, with an equal suddenness, he returned to poured abstraction. Even more curious, certain black images looked like crucifixions.

The mystery of these black paintings didn't directly affect "Lavender Mist," and I put my questions aside. But the puzzle returned a year later, in 1976, when I was talking with Tony Smith, the sculptor who is best known for his huge, black, geometric constructions. Smith had been a great friend of Pollock and of Barnett Newman, and I was asking him to design an installation for the Newman paintings to be shown at the opening of the National Gallery's East Building. This request was not as unusual as it may sound for, during the 1950s, Tony had helped Pollock and Newman install their shows, drawing on his skills as an architect, his profession before becoming a sculptor; indeed, Tony had served as Frank Lloyd Wright's clerk in New York.

At some point, we began discussing "Lavender Mist," and the events of the summer of 1950 when it was painted. Almost casually he added, "Oh, there was also the church Pollock and I worked on." "What church?" I asked, thinking of the crucifixion images. Tony paused, and said something like "It was only an idea." And the black paintings? "Oh, those came later." Tony would add nothing else except "Alfonso was also a part of it."

Alfonso was Alfonso Ossorio, the man who owned "Lavender Mist," and whom I was soon to meet in East Hampton to discuss its possible acquisition by the gallery. Ossorio, himself a painter and sculptor, had been Pollock's only real patron, at a time when Pollock sold almost nothing in spite of his fame. He could only tell me that "Yes, there was a church, a Catholic church we hoped to build on Long Island. Tony and Jackson and I discussed it at some length that summer--or at least, the concept of it. But what went on later, I don't know. I was away during the following year, in Paris. I do remember Tony and Jackson did a design for it. I don't know where it is. You should talk to Tony again."

I next mentioned the mysterious church to B.H. Friedman, a writer down the beach on Cape Cod and Pollock's biographer. He showed me the text of two Pollock letters to Ossorio in Paris, from January 1951--a date only five months before the black paintings. In one, Pollock wrote "nothing new on the church," while the other asks Ossorio, "Have you seen the Matisse Church and design?" referring to the jewel-box-like chapel in Vence, above the French Riviera, which Matisse had just finished. This was the first material directly from Pollock's hand indicating his interest in a church.

In January 1978, Tony came to Washington and we discussed many things, again, including the church. "What exactly was it?" I asked. "It evolved through many stages," he replied, "For example, I went to the premiere of Hans Namuth's movie on Jackson. You know, the one where he filmed Jackson painting on glass. After the movie I told Jackson how much I liked that part, and he asked me if he could do the windows in the church using a similar technique. We talked about it for a while."

But that was all I could find out. Although still puzzled, I had other things to pursue. Soon the East Building opened, with "Lavender Mist" on view only a short distance away from the Newman gallery designed by Tony. A short time later, I took a period of leave and went to France to start a long planned study of cubism. I came back with other projects as well. But last spring, the Centre Georges Pompidou in Paris asked me to work on the Pollock exhibition it was organizing to open this winter. I suggested the black paintings, especially as one of the key pictures, No. 14, had just been made a long-term loan to the gallery by Lee Krasner Pollock, the artist's widow.

But where to start again? Sadly, Tony Smith had died the previous winter. I wrote to Alfonso with the general idea of visiting East Hampton, and asked him to recall anything further about the church. I still believed the paintings and the church were linked in some specific way. Summer came and I left for a working vacation, taking my notes. Then, Alfonso called. He had found a plan of the church. Tony's plan.

I waited through three almost unbearable days of Cape Cod fog before I could fly to East Hampton. After seven years, I couldn't wait to see finally what the church looked like. But beyond that, I also looked forward to a visit with Ossorio, whom I hadn't seen since the gallery acquired "Lavender Mist." Then our negotiations had produced the kind of tension natural to that situation; but at the same time I was repeatedly moved by his deep commitment to Pollock and to his work.

We sat at a table on the terrace overlooking the Atlantic, and opened a large folio. I recall that my first response was shock. After years of my thinking about Pollock's thinking about Matisse's chapel, the Pollock/Smith church had become--in my mind--about the same small size. But the design in front of me showed a project of very large scale, a real church.

As with Tony's later sculpture, his architectural design was rigorous in its geometry. An elevation indicated the whole building raised up on posts--again something Tony would do in later sculpture. The plan showed a design based on equally sized hexagonal forms. The one center contains a skylight, divided into six parts raised to form a dome. Alfonso recalled that this was over the altar. Six hexagons, also with a six-part dome, were joined to the skylight, forming a kind of ring around it, and with a more central focus. By adding further hexagonal elements to this basic layout, Smith shifted the design to that of a traditional cathedral plan, with the units on this side forming transepts, while those at the ends serve as a narthex and vestry.

We paused from looking at the plan. Ossorio recalled it included a side chapel and a confessional. These we quickly identified, the chapel projecting outward, the confessional near the entrance at the narthex. One element was set apart from the other. Using architectural conventions as a guide, I guessed it was a baptistry. "Yes, that is what it was," said Alfonso.

Perhaps even more remarkable was that looking at the plan in detail revealed what Pollock was going to do. A repeated sign of squiggly lines showed 30 paintings to be mounted in the ceiling divisions. Six canvases would fit into the domelike vaults over the confessional, and another six would crown the side chapel. But in an extraordinary move, the remaining 18 were to the triangular elements around the skylight. The squiggly lines on the plan indicate the works would have been poured paintings, made on Pollock's studio floor and then mounted on the ceiling. I remember sitting back and thinking, "I'm in this warm Long Island sunshine, under the same light this church would have been in. Imagine that light coming in, surrounded by paintings like 'Lavender Mist,' which I've seen under this light, in the house directly behind me."

As I flew back, my mind was reeling under the power of this architectural and painting conception. As if by fate, three nights later at dinner I met Virginia Stotz, an art historian working on Tony's sculpture. She had been reviewing his unpublished papers, which constantly referred to the Pollock church. "Not only that," said Stotz, "but Jane, Tony's widow, and his studio assistant have a model they believe Tony made for the church."

At the end of the summer, I visited Jane Smith and saw the model. It matched the plan in every respect, and gave further detail that the baptistry was located on the ground--rather than on posts--and that the church was entered by a ramp. But the model revealed something more important. Around the outer walls at the center of the building was a series of windows, making a sort of modern equivalent to a medieval clerestory. This confirmed what I suspected; namely that Pollock's black paintings were indeed indirect sketches for windows: that the black figures painted on clear white canvas would be like black figures painted on clear glass. And that explained why they included crucifixion images.

This was further confirmed by something Alfonso had told me earlier in the summer. I had asked what happened to the church. "It was presented in the summer of 1952 to group of prominent Catholics. Jackson, Tony, Lee and myself were all there. It was badly received. Tony was furious. He picked up the model and stormed out. The idea of the church was done."

Had it been carried out, in whatever form, the church would easily have been the most important work in both scale and complexity for both artists.

Later, in the fall, Lee Krasner Pollock added more information about the fate of the church. She told me that following the meeting there were several requests to publish the plans for the church, including one from Life magazine. Tony refused all offers. His collaboration with Jackson was never published during his lifetime: I can now understand his reticence with telling me, as I came upon it.

As for Pollock, after the end of the church, he returned to poured abstractions; the "mysterious" black paintings were only made while the church was a possibility. A year later his working went into a sharp decline, and then stopped completely. He died in 1956.