WILLIAMSTOWN, MASSACHUSETTS.- Norman S. Hirschl, one of the two founders of the Hirschl & Adler Galleries in Manhattan, died at the age of 86. Hirschl & Adler Galleries was founded in 1952 by Norman S. Hirschl and Abraham M. Adler. In 1967 Stuart P. Feld joined the firm as a partner, and since 1982 has served as its President. Originally housed in the Marguery Hotel on Park Avenue, the gallery moved to a townhouse on East 67th Street in 1958, and in 1977 relocated to its current home: a handsome landmark townhouse at 21 East 70th Street. Today, Hirschl & Adler specializes in American and European paintings, watercolors, drawings, and sculpture from the eighteenth through the early twentieth centuries; American prints of all periods; and American decorative arts from 1810 to 1910. Its contemporary arm, Hirschl & Adler Modern, shows a comprehensive array of American and European art from the Post-War period. Each year, the gallery assembles about a dozen special exhibitions exploring historical and contemporary themes, or examining the work of individual artists, past and present.