Consulting psychologist. Horton was born in London in 1879 and received his early education in England, France, and Switzerland. After coming to America, his guardian, F.W. Holls, prepared him for entrance to Harvard, 1897, but upon the advice of Henry James Horton soon transferred to Williams College where he received his degree in 1901. He took his M.A., 1911, and Ph.D., 1922, at Columbia University. Horton's early work was with various railroads in a personnel capacity. He soon became interested in research in the fatigue and rest states and, ultimately, in dream psychology. During and following World War I, he studied shell shock and trench nightmare. Horton lectured and wrote widely on these subjects in addition to his consulting practice in Boston. He was the organizer of the Cartesian Research Bureau which evolved a precision method for the study of dreams. Horton is author of THE DREAM PROBLEM AND MECHANISM OF THOUGHT, 1925, and many articles in professional journals. Dr. Horton died January 19, 1945.

Many typescripts of Horton's lectures, research studies, articles, and professional case histories, material gathered by the Cartesian Research Bureau, and correspondence, chiefly professional. The correspondence is largely that of Samuel Dana Horton, father of Lydiard, and includes eight letters of Moreton Frewen, three each of Robert Todd Lincoln, John Fiske, and C.W. Fremantle, one of President James A. Garfield, and typescript copies of nine from Henry James. There are two letters from Dr. Horton to his guardian, Frederick W. Holls, and one each to Horton from William James and William Howard Taft. The remaining indexed correspondence is with colleagues and professional associates. Some of the case histories contain correspondence as well as documentary material. Also, a diary of Lydiard H. Horton for July to December 1896, and copies of excerpts from the diary of Samuel Dana Horton, 1860, photographs, newspaper clippings, and printed pamphlets.