Royal Microscopical Society. 147 



II. — Notes on the Micro-spectroscope and Microscope. 



By E. J. Gayer, Surgeon H.M. Indian Army. 

 (Bead before the Koyal Microscopical Society, March 5, 1873.) 



In continuation of my paper on " A New Form of Micro-spectro- 

 scope," read before the Eoyal Microscopical Society on the 4th 

 December, 1872, I would wish to add the following few remarks. 

 On a trial it will be found that the arrangement with the erector 

 placed in its usual position in the draw-tube, as described in the 

 above-mentioned paper, may have a low-powered object-glass substi- 

 tuted for the erector, and that a very useful combination will be thus 

 obtained for viewing the slit, and the object under examination, in 

 the same field. A small ring screw adapter is all that is required 

 to enable the object-glass to be screwed into its place at the end of 

 the draw-tube. This combination, without a slit, can also be used 

 when an erect image is required, as in dissections and arrangement 

 of objects on a slide when placed on the stage of the microscope : 

 and it will be found that, with this arrangement of two objectives, 

 the magnifying power can be diminished or augmented almost at 

 pleasure, without changing either of the object-glasses, by simply 

 altering the relative distances between the object under examination 

 and the first object-glass, and the distance between the first and 

 second objectives, so that almost any degree of magnifying power 

 which is found expedient, can be easily and rapidly obtained without 

 any alteration in the apparatus. The least magnification will be 

 obtained when the two objectives are near each other, and the 

 farther they are separated the more the image will be enlarged. 

 For those persons who have not got an erecting eye-piece, the 

 arrangement herein described will prove a useful and very cheap 

 substitute. It will also be found, if a micrometer of any convenient 

 construction be placed in the position of the slit in this form of 

 micro-spectroscope, and the arrangement just described be used, 

 that a very sharp image of the micrometer and the object on the 

 stage will be obtained ; and in some instances this plan will be 

 found more efficient than any of the usual forms which have, from 

 time to time, been adopted. I would also wish to suggest, that 

 when a micrometer with lines ruled on glass is used either in the 

 shape of a stage micrometer or that form which is placed in the 

 eye-piece, that, instead of having the lines ruled in the usual way, 

 they should be made up of concentric circles placed at equal dis- 

 tances from each other ; an object would in this way be very 

 readily measured in all its diameters, and facilities for making 

 drawings would also be afforded. Since my paper of the 4th 

 December was read, it has been brought to my notice that the 



