349 



On the Evolution of the Microscope. 

 By Edward M. Nelson, P.R.M.S. 



Your Committee, having thought that an impartial account 

 of microscopes and apparatus published in your Journal from 

 time to time would, by enabling students to thoroughly under- 

 stand and scientifically appreciate the various parts and move- 

 ments of modern microscopes, not only benefit the members, 

 but also fulfil one of the primary intentions in the foundation 

 of this Club, have appointed a Sub-Committee to report on 

 the matter. 



The Sub-Committee have come to a unanimous conclusion 

 that as one of the means of guidance for the future is a study 

 of the errors of the past, the end will be best served by (a) a 

 thorough investigation of a good type of instrument designed 

 at some period subsequent to the introduction of achromatism, 

 tracing the development of its various parts from the earliest 

 times, (b) A study of modern instruments, showing wherein 

 and why they either follow or depart from the selected type, 

 (c) The collation of other material bearing on the development 

 of modern microscopes though not falling within the limits of 

 a and b. 



The first step, then, was the choice of a type ; in this the 

 Sub-Committee had little difficulty, for the type must obviously 

 fulfil two conditions. (1) It must be that towards which the 

 modern microscope is tending. (2) It must be a permanent 

 form. 



There is only one microscope in which both these necessary 

 conditions are to be found, and that is Powell's No. 1, for it 

 requires the slightest observation to perceive (1) that the best 

 modern microscopes are more and more conforming to that 

 type, and (2) that it has remained in its present form for up- 

 wards of twenty years. 



Our first duty, then, is to lay before you all the causes 

 accumulated since the invention of the microscope, that 



