JOUENAL 



OF THE 



ROYAL MICROSCOPICAL SOCIETY. 



SEPTEMBEE, 1921. 



TRANSACTIONS OF THE SOCIETY. 



IX.— SOME ABBE LETTERS. 

 Eead by Pkofessor Cheshire, C.B.E., F.Inst.P., F.E.M.S. 



{June 15, 1921.) 

 Four Text-Figures. 



Introduction. 



SOiME time ago, my friend, Mr. Harrison Glew, presented me with 

 a number of letters (holograph) written by the late Professor Abbe, 

 and addressed to the eminent English microscopist, John Ware 

 Stephenson, who was as you know, an honoured Fellow, and at 

 one time Treasurer, of this Society. 



The three letters which I propose to read to you to-night, 

 although written nearly half a century ago, deal with the Abbe 

 diffraction theory of microscope vision in such a clear and delight- 

 ful way, that I suggested to our late President — Mr. Barnard — 

 that they should be read at one of the Meetings of our Society, 

 and placed upon record in the Proceedings as a matter of historical 

 interest. To this suggestion he gave e cordial assent. 



Xow these letters were written in December 1876, whilst 

 Abbe's theory was still hot on the anvil, and in fairness to Abbe, 

 this fact should be borne in mind. A man deals with his theories 

 in letters, the publication of which he does not contemplate, with 

 a freedom of thought and expression which he Avould scarcely 

 commit himself to in a paper written for a Society. This con- 

 sideration, however, I think it will be agreed, enhances the interest 

 of the letters. 



I have gone through the letters very carefully, but beyond 

 correcting a few — singularly few — slips of the pen, and removing 



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