This is a scientific treatise, chiefly relating to the computation of orbits in astronomy. HARTKEMEIER, HARRY PELLE, _Principles of Punch-Card Machine Operation_ (Subtitle: _How to Operate Punch-Card Tabulating and Alphabetic Accounting Machines_), New York: Thomas Y. Crowell Co., 1942, 269 pp. This is based on the author’s experience in teaching statistical analysis using IBM tabulators. The book does not deal with the collator or multiplying punch. HEDLEY, K. J., _The Development of the Punched-Card Method_, Actuarial Society of Australasia, 1946, 20 pp. INTERNATIONAL BUSINESS MACHINES CORPORATION, _International Business Machines_ (form no. A-4036-6-45), New York: International Business Machines Corporation, 1945, 65 pp. Pages 6 to 31 show pictures and brief descriptions of about 20 punch-card machines, available in 1945. SCHNACKEL, H. G., and H. C. LANG, _Accounting by Machine Methods_, New York: Ronald Press Co., 1939, 53 pp. WOLF, ARTHUR W., and EDMUND C. BERKELEY, _Advanced Course in Punched Card Operations_, Newark, N. J.: Prudential Insurance Company of America, 1942, 98 pp. A useful and authoritative description of IBM punch-card calculating machinery is the following: INTERNATIONAL BUSINESS MACHINES CORPORATION, DEPARTMENT OF EDUCATION, _Machine Methods of Accounting_, Endicott, N. Y.: International Business Machines Corporation, 1936-41, 385 pp. This is a collection of 28 separate booklets telling the detailed operation of IBM punch-card machinery. They were written for employees of IBM and users of IBM equipment. The following list of the booklets is useful in locating them: