To the Editor: —In the article by Dr. D. G. Healy, on "A Comparison Ocular" (The Journal, Nov. 29, 1913, p. 1958), stress is laid on the date since which it has been used (May, 1912), and it is stated that the instrument has been constructed by Messrs. Bausch & Lomb, from the idea suggested by Dr. Healy. Furthermore, it is stated that it antedates by six months the comparison microscope devised by Dr. Thoerner in Germany. The Comparison Ocular described, is not new but is over twenty years old. It was made by C. Reichert, Vienna, on the suggestion of Dr. Henri von Heurck. It is fully described on pages 105 and 106 in his book, "The Microscope, its Construction and Management." The English edition was published in 1893 by Crosby Zockwood & Son, London, England, and the D. Van Nostrand Company, New York. [The foregoing letter was referred