Harriet Vaughn Davies, 99, who grow up on a sailing ship and became a social worker, a university administrator and an author, died of pneumonia Saturday at a hospital in Austin, Tex.

She was born in Baltimore and spent the first 16 years of her life aboard the Lizzie Ross, one of the last of the square-rigged cargo vessels. Her father was the captain and he insisted on having his family at sea with him.

Mrs. Davies wroted a book about her girlhood called "Aboard the Lizzie Ross." It was published in 1966 when she was living in Washington with her daughter, Elspeth, and son-in-law, Walt Whitman Rostow, who was then a special adviser to President Johnson on foreign affairs.

Her days at sea ended when her father, Capt. John Albert Vaughn, decided that he should establish a home on land so that his daughter and two sons could go to college.

Mrs. Davies graduated from Bucknell University and then became a social worker in Baltimore. She later married Milton Davies, who established the Academy of Arts and Sciences at Columbia University in New York. When Mr. Davies died in 1926, Mrs. Davies went to work for the Columbia University Extension, the university's adult education program, as adviser to women. She was, in effect, the program's dean of women. She retired about 1945.

After her daughter married Rostow in 1947, Mrs. Davies made her home with them. She accompanied them to Geneva, Switzerland, Cambridge, England, and Cambridge, Mass., where Rostow was a professor at the Massachusetts Institute of Technology, and then to Washington for eight years, when Rostow was an adviser to President Kennedy and Johnson.

Since 1969, she has lived in Austin, where Rostow is professor at the University of Texas.

In addition, to her daughter, of the home in Austin, Mrs. Davies is survived by two grandsons.