On October 14, 1970, an explosion ripped through the attic of a stately brick building on Divinity Ave. Activists protecting the war in Vietnam had planted a tomb in Henry A. Kissinger's former office at the Center for International Affairs, housed in the Harvard Semitic Museum.

Kissinger had long since gone, and the damage was limited--but the blast's impact was far from insignificant. The museum had closed its doors to the public 28 years earlier, and many of its treasures lay forgotten in its dusty storage rooms.

As Curator Carney E. V. Gavin sifted through the blast's aftermath, however, he discovered a long-lost photographic collection that would spur the museum's revival and prompt one of its most ambitious projects in decades.

Packed in dozens of faded crimson boxes were 28,000 photographs of the Middle East by well-known 19th century photographers.

Ten years after Gavin's find, a local physician and amateur photographer traveled to Israel to retrace the steps of the 19th century artists. At Gavin's suggestion, Dr. Daniel Tassel set out to create a "then and now" photographic history of the Holy Land. Nitza Rosovsky, a museum officer and authority on 19th century Jerusalem, assisted Tassel with the project.

By the spring of 1983, Tassel had shot enough photographs to allow a preliminary showing of his exhibit. "The Holy Land Then and Now," at the Semitic Museum. An expanded form of the exhibit moved to Israel in 1984, where it is currently on display at the Haifa Museum.

The photographs depict historically significant sites and panoramic views of Israel's landscape.

"We immediately adopted the project and began perusing through the pictures freed by the bomb blast. We selected images that, by virtue of their innate beauty, historical interest, or charm were particularly appealing to us," Tassel says.

Among the works chosen by Tassel and Rosovsky were a number of prints by the French Bonfils family. Felix Bonfils, who settled in Beirut, began a well-known collection of photographs in 1967.

Like most of his contemporaries, Bonfils suffered from the combination of primitive photographic techniques and the oppressive climate of the Middle East. "He often looked on in frustration as his photographic chemicals fizzled away before his eyes," Rosovsky says. Despite the adverse conditions, "he and his family produced thousands of beautiful works," she adds.

Rosovsky and Tassel also selected several photographs by Francis Frith, a greengrocer who left his, shop in Liverpool in 1858 to take pictures of the Holly Land, and others by Sgt. James McDonald, who made his "Ordinance Survey of Jerusalem" for the British Army in 1857.

"Accompained by pocket-sized copies of the 'then' photos, which I had made to help select the best vantage point for my 'now' photos, and by Nitza's location instructions, I began to photograph in Israel in the summer of 1981," Tassel says.

During three trips to Israel, Tassel shot thousands of rolls of film, which later yielded hundreds of prints and dozens of "then" and "now" pairs.

When his 19th century predecessors attempted to photograph the Holly Land, they met unexpected resistance, Tassel says. As Christians, they did not understand the hostility of the native Arabs and Jews who were forbidden to create "graven images," he explains.

A century, later, Tassel met a more hospitable reception. "When I began to photograph, human barriers disappeared. Christians, Moslems and Jews, the ordinary and the more sophisticated--all were awed by the pocket images of their homes, shops, or places of worship as they looked 100 or more years ago," he says.

Tassel's quest to reproduce the original images as accurately as possible led him from hillsides to rooftops and from the seaside to the desert. After three trips to Israel, Tassel says, he began to develop a "sense of identify" with the early photographers. "I often knew that I was photographing from the exact spot chosen by my predecessor, but my appreciation deepened as I realized that he had not only selected the aesthetically pleasing viewpoint, but also the most obvious place to rest his cumbersome equipment."

His photographs illustrate a history of change, but also of continuity. "Some of the places had changed dramatically. Others had changed so little that I caught myself almost confusing 'now' with 'then,'" he says.

Tassel points to a pair of pictures of Jerusalem. Bonfils shot one of them over 100 years ago; Tassel shot the other two years ago. With the exception of a few trees and buildings in the foreground of Tassel's print, the two photos are almost indistinguishable. A domed Moslem shrine dominates the parched landscape of the walled city, little changed through the centuries.

By way of contrast, the doctor displays another pair of pictures which bear only the slightest resemblance to one another. Both photographs depict Tiberias, a coastal city in Northern Israel. They were taken from the exact same location but separated by 100 year's time. Only an ancient tower, present in both photos, helped Tassel find the spot where Frith rested his camera in 1858.

The city, which has been destroyed and rebuilt several times, became the temporary center of the Jewish religion in 70 A.D., when the Roman army sacked Jerusalem.

"What I find most incredible is that some of my photos actually show more complete views than the old ones," says Tassel, pointing to his shot of Jerusalem's Damascus Gate, which faces the Syrian capital to the North. Due to modern archaeological excavations, the contemporary picture shows more of the ancient structure than the Bonfils original.

The gate was originally built by the Romans as part of the defensive wall around Jerusalem and served as one of several entrances to the city. The gate visible today was built on top of the Roman gate in the mid-16th century by the Turkish Sultan Suleiman the Magnificent, but recent diggings have revealed parts of the old gate, Rosovsky says.

The ravages of war have completely altered other sites of historical interest, obliterating ancient landmarks such as Jerusalem's Hurva Synagogue. The temple was the subject of an 1867 photograph, but only a reconstructed arch can be seen in Tassel's counterpart.

An Arab bomb leveled the structure during Israel's 1948 war for independence.

Noting that he has witnessed other changes in the land during his own travels. Tassel says his work is part of a continuum: his "now" pictures will eventually become "then" pictures for other photo-historians.

Rosovsky, who helped Tassel throughout the project, describes the amateur photographer as a perfectionist. "He made three journeys to Israel--all on his own time and with his own money--to capture the same feeling in his photographs as in those taken a century before," she adds.

After collecting thousands of feet of film, Tassel processed the photographs in the darkroom of his Lexington, Mass., home. The portfolio is still evolving. "I don't know if it'll ever end," Tassel says.

At the invitation of Jerusalem Mayor Ted Kollek, the exhibit will journey to Jerusalem this fall as part of a celebration marking his 20th year as mayor. Kollek saw the exhibit last spring when he visited Harvard to receive an honorary degree.

In 1986, "The Holy Land Then and Now" will return to its permanent home, the Semitic Museum.