Gellatly was born in 1853 in New York City, the son of Peter N. Gellatly of Scotland and his Irish wife. His parents died when he was a youth, and he was brought up by his uncle, William A. Gellatly, who was a partner in the drug firm of W. H. Schieffelin & Company.
Gellatly worked in the drug firm of W. H. Schieffelin & Company from 1871 to 1884. At one time he represented the firm in London. From 1885 to 1916 the directories of New York City listed him as conducting an insurance and real estate business. During his married life, together with his wife, they were ardent collectors of paintings and other works of art, having a special gallery at their house at 34 West Fifty-seventh Street. Her estate listed 206 paintings; 34 still remain in the collection as well as some fifty other works of art which are listed in the inventory of her estate. In the next fifteen years Gellatly made many changes in the collection, which, in 1928, was moved to the Heckscher Building, Fifty-seventh Street and Fifth Avenue. At that time it was practically complete. Early in 1929 the collection was offered to the Smithsonian Institution for the National Gallery of Art and was accepted on June 13, 1929. On April 30, 1933, it was taken to Washington and was opened with a reception on June 22, 1933. Gellatly did not live to see the collection installed in Washington. The collection consists of 1, 640 items: American and foreign paintings; Chinese antiquities; Syrian, Egyptian, Greek, Roman, and Arabic glass, and necklaces; sixteenth-century jewelry, East Indian art objects; French, German, Gothic, and American sculpture; furniture; stained glass; cameo glass; textiles; Battersea enamels; and many other classes of objects. Gellatly's special interest was the works of contemporary American artists. The works of these form slightly more than sixty percent of all the paintings. There are 56 known and 7 unknown artists represented with 164 paintings. Many of the American paintings were purchased directly from the artists themselves. Such foreign artists as Rubens, Van Dyck, Puvis de Chavannes, and Piazzetta are also represented. While especially interested in the American artists, Gellatly bought only works which he believed to be beautiful. In fact, when acquiring glass, enamel, pottery, furniture, jewelry, or other objects he gave consideration only to those things that were in harmony with the rest of the collection. He did not confine himself to any time or country but drew from all times and nearly all sections of the world. Beauty and craftsmanship were the requirements which he rigidly followed in his world-wide outlook. Gellatly died of pneumonia in New York City.
While studying in an art school, Gellatly met Edith Rogers, who, in 1886, became his wife. She was the daughter of Columbus B. Rogers, a lawyer, and niece of Jacob S. Rogers, president of the Rogers Locomotive & Machine Works of Paterson, New Jersey. She died on July 17, 1913. On September 24, 1930, Gellatly married Mrs. Charlyne Whiteley Plummer.
