NOTE. Any THESE lectures were given at the Lowell Institute, Boston, in November and December, 1890. student of the subject will at once perceive my obligation to the textbooks of Professor A. S. Hill, Professor Bain, Professor Genung, and the late Professor McElroy. My excuse for offering a new treatment of the subject is that I have found none that seemed quite simple enough for popular reading. BOSTON, September, 1891. B. W. |