JOURNAL 



OF THE 



ROYAL MICROSCOPICAL SOCIETY 



FEBRUARY, 1905. 



TRANSACTIONS OF THE SOCIETY. 



I. — TJie Tlieory of Highly Magnified Images. 



On the Diffraction of an Object-Glass with Circular Aperture. By Sir 

 George B. Airy. Philosophical Transactions, vol. v. p. 283. 



The Theoretical Limits of the Besolving-Power of the Microscope. By 

 Professor Helmholtz. Poggendorjfs Annalen, 1874, Jubelband, p. 569 ; 

 Wissenschaftliche Abhancll ungen , vol. ii. p. 185. 



On the Theory of Optical linages, with special reference to the Microscope. 

 By Lord Bayleigh. Philosophical Magazine, 5th scries, vol. xlii. 

 p. 167 ; Journ. B.M.S., 1903, p. 447. 



On the Theory of Optical Linages, with special reference to the Microscope. 

 Supplementary paper. By Loi'd Bayleigh. Journ. B.M.S., 1903, 

 p. 474. 



By J. W. Gordon. 



(Read December 21st, 1904.) 



Synopsis. — For the convenience of readers who may like to 

 have the theory of high magnification in a very compendious form, 

 the following synopsis of this paper is submitted : 



I. The image formed by any aperture of a luminous point is 

 an illuminated area, the shape and dimensions of which depend 

 upon the form and size of the aperture (Airy, p. 5). 



II. The focussed image of such a point is an antipoint, the 

 shape of which is derived from the shape of the aperture by a rule 

 of inverse resemblance, so that the antipoint is narrow across any 

 diameter across which the aperture is broad, and vice versa. Tins 

 rule of inversion results, in the case of a symmetrical aperture, in 

 an approximate reproduction by the disc of the antipoint of the 

 form of the aperture turned through an angle of 90' (Airy, p. 5). 



III. In the case of a circular aperture, transmitting a beam in 

 which the light arrives at the aperture in the form of plane wave- 



Feb. 15th, 1905 B 



