On the upper stretch of this boulevard are the magnificent ménages of Mrs. Mary Duke Biddle, Dr. A. Hamilton Rice, Mrs. Hamilton McTwombly, Mrs. William Hayward, Julia Berwind, Mrs. W. Watts Sherman, and the garden-enclosed, garishly grandiose show-place of the late Andrew Carnegie. The Carnegies are not gregarious and few fashionables have seen the interior. Set in between them, in a regal mansion once owned by Whitney Warren, a society architect, and designer of Grand Central Terminal, was an all-night "bottle club" that dispensed liquid refreshment after closing time to a favored few. On Riverside Drive, the gingerbread château of the late Charles M. Schwab which long stood empty has also been torn down. The Schwabs were not social, but musical. Their Sunday afternoon concerts when Melba, Tetrazzini and other prima donnas sang, were discussed even in Europe. At 1 East 78th Street, on the corner of Fifth Avenue, is the white marble palace of Mrs. James B. Duke, mother of Doris. This great house has a magnificent collection of 18th century English paintings and drawings. The Harrison Williamses live at 1130 Fifth Avenue. The beautiful Mona entertains there against a distinguished background of paneled rooms, her portrait by Dali, and several Goyas. The Byron Foys live at 60 East 93rd Street, in one of the finest houses in the city. Built by Mrs. Graham Fair Vanderbilt, it has the most beautiful French 18th century paneling. On its walls are portraits by great masters as well as family portraits painted by Simon Elwes. But most socialites live in vast apartment houses or hotels. To see them in the flesh, one can peep in several restaurants. Tops is the Colony, on East 61st Street, just off Madison. It serves wonderful food at wonderful prices. Strangers find it difficult to get reservations. If one does, he will be far back, in the main room. Many regulars prefer it there, though, and you may land next to Winthrop Rockefeller, Baron Maurice de Rothschild, Clark Gable, or, while she was here, you might have encountered Princess Martha of Norway. Table No. 1, at the right of the entrance, was long reserved for the William K. Vanderbilts. After his death, his widow never returned. Now one is apt to find at this spot the Duke and Duchess of Windsor, Mme. Frances, the Alfred Sloanes or young Lord Lascelles. Table No. 21 is bachelor-girl Beth Leary's hangout. At No. 14, Mrs. George U. Harris and her charming daughter, Lucille, are on view. No. 34 is where Elsa Maxwell, Clare Boothe Luce or Dorothy Thompson sit, but not together. Table No. 4b is given to the Vincent Astors, to Lady Furness, or to society reporters. Voisin is smart, but far more conservative, and none of the faces would mean anything to the uninitiated. To El Morocco goes the International Set.