356 THE PRESIDENT'S ADDRESS. 



third device is one to whicli your attention has been called bef or e. 

 A diagonal piece of looking-glass is fitted in an eye-piece cap, 

 the microscope placed in a horizontal position, and the image 

 projected on a piece of paper, where it can be drawn without 

 the necessity of looking through the microscope, camera, or 

 other apparatus at all. 



With regard to the theory of the microscope I am glad to be 

 able to report that the views expressed here in connection with 

 the diffraction theory have been accepted in toto. You will 

 never again hear of the futility of the microscopical examina- 

 tion of the P. angvlalum, or of the stopping out the useless 

 central beam, or the prediction of intercostals solely from the 

 consideration of first order spectra, or that diffraction begins 

 at '01 mm. 



The review of the microscopical work in my own depart- 

 ment during the past few years is now finished, and, therefore, 

 that which may be termed the official part of my address is 

 closed; but as it has been the growing practice to shorten these 

 presidential reviews and supplement the address by some origi- 

 nal w^ork, my photomicrographic apparatus, which has not been 

 exhibited or described before, is brought for your kind inspec- 

 tion this evening. During my microscopical career, of which 

 this is the 24th year, it has been my earnest endeavour, 

 by work and long acquaintance, to understand as far as 

 possible any instrument or theory before writing about it. 

 Such a line of conduct is not in keeping with the procedure of 

 the present day. 'Now a man (he cannot be called either a 

 worker or an observer) buys a microscope, and a fortnight after- 

 wards writes a book upon the subject, an article or two in the 

 periodicals from the same pen having appeared in the interval. 

 Bad as this is among ourselves, it is as nothing in comparison 

 to that which goes on in the photographic world. The injury 

 caused by this system is considerable, because it often happens, 

 especially in periodicals, that an extremely valuable paper does 

 not receive the attention it deserves, on account of the vast 

 accumulation of rubbish by which it is surrounded. This, 

 however, is a digression. But to return to our subject, I 

 began photomicrography upwards of ten years ago, consequently^ 

 before the advent of apochromatics. The apparatus then made 

 from my design was not precisely similar to any published 



