“Optical Glass” and Fluorite: an Ethical Note

Abstract

MR. F. J. CHESHIRE'S letter in NATURE of March 30 recalls the most exceptional character of the publication by Prof. Abbe and the firm of Zeiss of that discovery of apochromatism for which all must still be grateful. For the details I refer to the Journal of the Royal Microscopical Society, ser. 2, vols. vi., vii., 1886–7. An article in vol. vi., p. 315f, “The New Objectives”, is evidently based on the letter of Prof. Abbe of March 4 (cited by Mr. Cheshire), for it contains precisely the same window-dressing statement that, optical glasses hitherto in use only contain six chemical elements, while the new objective contains not fewer than fourteen. This article throughout conveys the impression that it has been alone the utilisation of new kinds of glass that has enabled Abbe to work out the conditions of practical apochromatism.