214 president's address. 



It is a fallacy lying at the root of elementary optics to 

 suppose that any real increase in the working power of the 

 microscope can be obtained by subjecting the primal image of 

 an approximately perfect object-glass to examination by a 

 second microscope or complex combination of lenses. It has 

 been tried with blank failure as the result, sufficiently often, one 

 would have supposed, to have prevented its recurrence now, 

 when the optics of the microscope have something like a 

 complete form. 



The magnifications, so-called, are of necessity " empty " and 

 valueless. All they can do is to enlarge the details of the 

 microscopic image which has been brought about by diffraction 

 in the first objective, and, therefore, there cannot, by any 

 possibility, be a single detail added, while the details that the 

 accurate image does disclose must be blurred and tortured 

 tenfold more than when subjected to the legitimate action of 

 well- constructed eye-pieces. 



It will never be by means of mere enlargement of the primal 

 image that progress will be made in increasing the powers of 

 the microscope. This can only be done by increasing the 

 capacity of the object-glass to grasjD a larger area of diffraction 

 fans, so as to enclose within the image all that is produced by 

 the object ; and to that we must look in the future for the only 

 legitimate means of penetrating farther into Nature's details. 



Another curious error is presented during the year in quite 

 another way. In a book* by a very respected continental 

 author, which sets itself the task of making simple to the 

 uninstructed the entire diffraction theory of microscopic vision 

 and the practical use of the instrument, there is an inexplicable 

 misinterpretation, or, at least, misapplication of the very theory 

 itself. 



By all who have mastered the doctrine of diffraction in its 

 application to microscopic objectives, as enunciated by Abbe, 

 it is unmistakably understood to be an inference from that 

 diffraction theory that wide apertures should accompany high 

 amplification, and that moderate aperture should be the accom- 

 paniment of moderate and low amplifications. Abbe says that 

 " a proper economy of aperture is of equal importance with 



* " The Microscope." By Dr. Van Heurck. Translatsd b_v Wynne E. 

 Baxter. Crosby, Lockwood, and Sou, London, 1893. 



