JOUBNAL 



OF THE 



ROYAL MICROSCOPICAL SOCIETY.. 



FEBRUARY, 1907. 



TRANSACTIONS OF THE SOCIETY. 



I. — The Use of a Top Stop for Developing Latent Powers of 



the Microscope. 



By J. W. Gordon. 



{Bead November 21, 1906.) 



PliATES I., II. AND III. 



In the course of the last session I had the honour of bringing to the 

 notice of the Society a piece of apparatus designed to enable an 

 observer to place a stop in the Eamsden circle of a Microscope, 

 for modifying the illumination of the image formed by the instru- 

 ment.* At that time, however, I could speak only as a matter of 

 theory of what might be expected from the use of the instrument, 

 the apparatus itself having 1 )een but a very short time in my hands. 

 During the vacation I have found some opportunities of bringing 

 it into experimental use ; and in the hope that my results may 

 be of some interest to Fellows of the Society, I have prepared a 

 selection of photographs for subndssion to this Meeting. 



Of the apparatus itself it is not necessary to give a detailed 

 description here, seeing that the main parts of it have been both 

 described and figured in the pages of the Society's Journal. 

 These comprise a supporting collar, which can be clamped to 

 the draw-tube of the Microscope, a screw-pUlar carried by tlie 

 collar, and supporting in its turn a stop-carrying arm and fine- 

 adjustment mechanism for moving the stop over the top of the 

 eye-piece, and holding it in any required position in the Eamsden 

 circle. The stops which I have used are formed by minute 



* See this Joui'nal, 1906, p. 157 ; see also p. 365 for a diagram of the apparatus 

 here in question. 



Feb. 20th, 1907 B 



