Abstract
LONDON. Royal Microscopical Society, June 19.—Mr. William Carruthers, F.R.S., president, in the chair.—Mr. T. H. Powell exhibited Coscinodiscus asteromphalus under a new 1/40th inch apochromatic oil immersion objective.—Mr. J. W. Gordon read a paper entitled “An examination of the Abbe diffraction theory of the microscope,” in which he stated that the above long-accepted explanation of the phenomena of high-power microscopic observation had been accepted on insufficient proof and would not bear the test of critical examination. The Abbe theory claimed that pictures formed by the microscope of very minute objects were due to diffraction images originated by the object, and that when the oblique rays of light in which these diffraction images existed were excluded, no image of the object was possible. This theory had been experimentally illustrated by Prof. Abbe by means of a grating on the stage of the microscope and a series of diaphragms behind the microscope object glass with slits to partially exclude oblique rays. Mr. Gordon showed that although in favourable circumstances diffraction effects were produced by fine objects on the stage of the microscope, these effects did not appreciably influence the formation of the image. He also showed that the experimental results produced by the above-mentioned diaphragms, which were adduced to prove the theory, were due to a diffraction effect produced by the diaphragms themselves and not by the grating on the stage of the microscope, the same results being obtamed with an aërial image of a grating projected upon the stage by a lens in place of the actual grating. He maintained that in the microscope, as in the telescope, it was necessary to eliminate diffraction effects as far as possible by making lenses of large aperture, and not, as in Abbe's theory, to include as many diffraction phenomena as possible. Diagrams in illustration of the paper were thrown upon the screen, and the various experiments referred to were exhibited under a number of microscopes. In the discussion that followed, Prof. S. P. Thompson agreed with Mr. Gordon in rejecting the presentation of the Abbe theory given by Naegeli and Schwendener, but found himself at variance with Mr. Gordon on almost every other point, and proceeded to discuss several conclusions arrived at in the paper.
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Societies and Academies . Nature 64, 320 (1901). https://doi.org/10.1038/064320a0
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DOI: https://doi.org/10.1038/064320a0