David Turnbull, at 92; taught physics at Harvard University

David Turnbull's early road to a doctorate and a faculty position at Harvard University was at times too muddy to navigate with the Model T he drove in the late 1920s. When that happened, he walked 8 miles to high school.

"We led quite a cloistered life, rarely venturing more than a few miles from home," he wrote of his youth on a 400-acre farm in northwest Illinois. "We had no radio until I was age sixteen, and I never entered a movie theater until my second year of college."

A member of the National Academy of Sciences, he focused his research on areas such as the crystallization of liquids and the diffusion of atoms in crystals. Dr. Turnbull died in his Cambridge home on April 28. He was 92 and had been diagnosed with Parkinson's disease.

Dr. Turnbull was awarded a Franklin Medal from the Franklin Institute of Science in Philadelphia and the Japan Prize for his achievements in science. In 1992 the Materials Research Society, a researchers' organization based in Warrendale, Pa., established an annual lecture in his name.

Although Dr. Turnbull's field was applied physics, he had "an extraordinary range of interests, a library loaded with history books, theology, and many, many biographies, heads of state, primarily," said his son Lowell of Chevy Chase, Md. "And he loved mysteries, too."

A career as the Gordon McKay professor of applied physics at Harvard was hardly what Dr. Turnbull envisioned as a boy in Elmira, an Illinois town that posted a population a bit shy of 400 in the 2000 Census.

"I would have preferred to spend my life operating our farm, but an asthmatic condition, which became apparent when I was two, greatly impaired my ability to perform certain essential tasks," he wrote in an autobiography that is posted on the Materials Research Society website, mrs.org. "By the time I completed high school, it was clear that I would have to find some career other than farming. In the post-Calvinist milieu of my home, it was taken for granted that any career should be directed toward human betterment, as it was understood."

The grandson of Scottish immigrants, he was 15 before his family switched from farming with horses to using a tractor. His father was a high school graduate who ran the farm with strength and courage in the face of large farm animals. His mother attended Oberlin College for two years and tutored her eldest son through dyslexia.

The family "belonged to a strict Presbyterian sect," Dr. Turnbull wrote, and "at home the Bible was read aloud, one chapter each morning, serially from Genesis through Revelations. . . . Admiring my father I wanted to accept his beliefs, but I became skeptical of them quite early."

Though he forged a career in science, Dr. Turnbull wrote that in his early teens he began "to admire the exalted ethical ideas of Jesus and for a time tried, I'm afraid with little success, to live up to them."

Jesus as a historical figure remained a lifelong source of fascination to Dr. Turnbull, his son said.

He graduated from Monmouth College in Monmouth, Ill., and received a doctorate in physical chemistry in 1939 from the University of Illinois at Urbana- Champaign. During World War II, Dr. Turnbull was on the faculty of what was then the Case School of Applied Science and met the woman he would marry in 1946, wooing her during long bicycle rides through Cleveland. Carol M. Turnbull died in 1999.

Dr. Turnbull began working with General Electric's research laboratory in Schenectady, N.Y., after the war ended and taught nearby at Rensselaer Polytechnic Institute. Recruited to teach at Harvard, he moved to Cambridge in 1962. In his autobiography, he noted that switching to academia meant taking a pay cut of about 40 percent, but at GE he "had been generously compensated and saved enough so that my family lived comfortably on the lesser income."

"The focus on Calvinist values and hard work, which was necessary to survive, stayed with him his whole life," his son said.

While at Harvard, Dr. Turnbull did research at institutions such as Cambridge University in England, Stanford University, and the Los Alamos National Laboratory.

He also switched his Major League Baseball allegiance.

While growing up on the farm, "once a year they would take the livestock to the Chicago stockyards," his son said. "My grand father used to take my father to the White Sox before they hopped the caboose home. Then he transferred his allegiance from the White Sox to the Red Sox when he came to Boston."

For many years after reaching the mandatory retirement age of 70, Dr. Turnbull regularly visited his Harvard office as professor emeritus. Near the end of his autobiography, his view of what he had learned seemed to echo some lessons from farm life long ago.

"I am impressed ever more deeply by the natural order, which seems remarkable and awesome," he wrote. "It can be described by science, but its existence and origin are still a great mystery which seems beyond our capabilities to resolve. For me it is not necessary to accept some metaphysical solution of this mystery; it is enough that the order exists and is esthetically pleasing."

In addition to his son Lowell, Dr. Turnbull leaves another son, Murray of Cambridge; a daughter, Joyce McDonald of Summerville, S.C.; and four grandsons.

A service will be announced.