JOUBNAL 



OF THE 



ROYAL MICROSCOPICAL SOCIETY. 



APEIL 1887. 



TEANSACTIONS OF THE SOCIETY. 



V. — The President's Address. 

 By the Eev. W. H. Dallinger, LL.D., F.E.S., F.L.S., &c. 



{Annual Meeting, 9th February, 1887.) 

 Plate VI. 



In proceeding to fulfil the honourable duty that by your courtesy de- 

 volves upon me, I purpose in the main to follow the line I have taken 

 in preceding years. I congratulate the Society on its work, and on its 

 steady influence in promoting progressive improvements in the optical 

 and mechanical construction of the Microscope, devoid of all prejudice as 

 to how, or from whence such improvements may come. And whilst 

 happily it is not of necessity a President's duty to pass in cursory review 

 the microscopical work of the year, there are times when it may be well 

 for him to review the points of improvement that have been made in the 

 instrument itself. 



For the past twenty years I have had an increasing interest in the 

 continuous improvement of the optical appliances of our instrument ; an 

 interest which, from the first, apphed not only to objectives, but also to 

 eye-pieces and condensers, which consecutive calculation, thought, and 

 experience have shown to have a correlated importance. 



Eighteen years ago I had by practice made myself fairly master of a 

 1/25 in. objective of that period, made by Powell and Lealand. I still 

 possess that lens, and it is as good a lens of its class as they ever con- 

 structed. 



Soon after I became equally familiar with a 1/50 in. of the same 

 class by the same makers. 



By saying that I became master of these lenses, I mean that I dis- 

 covered exhaustively what they would and what they would not do. By 

 this I learned definitely what I wanted in lenses if I could get it ; and 

 to get that has been my unceasing endeavour until now. And certainly 

 the quest has not been vain. And my method has been to examine 

 impartially, and possess myself of, EngHsh, Continental, or American 

 lenses, whenever they have showed any capacity for doing best what my 

 work proved to me required to be done. 



1 know that in estimating the quality of a lens by the class of image 

 it afi'ords of certain test objects well known to us, a certain amount of 

 empiricism must take place. We do not absolutely know the image it 

 ought to present. But this applies only within very narrow limits. 



1887. o 



