Simple Form of Spectroscope and Micro-spectroscope. 229 



14,000 lines per inch, is then placed between two micro-cover- 

 glasses, these being placed immediately over the eye-lens, the cap 

 of the eye-piece serving to keep them in position. That completes 

 the micro-spectroscope. 



Fig. 28. — D, diaphragm ; G, grating ; S, slit. 



The parts of the object to be examined are moved on the object- 

 stage so that their image falls on the slit in the eye-piece diaphragm. 

 They are then seen in the Microscope with their spectra next to 

 them, exactly as in the case of the hand apparatus above described. 



Although unnecessary for the purpose for which I have been 

 using the micro- spectroscope, it would seem best for general 

 purposes to arrange for the one jaw of the slit to be removable, or, 

 rather, to be able to pull it out of the field of view, or push it up 

 to the other one through an opening in the eye-piece tube. In 

 this way a large part of the object specimen will be in full view, 

 and the part to be spectroscopically examined can be conveniently 

 moved to the position of the slit before closing in the other jaw. 



A very convenient plan would be to have an entirely removable 

 slit, which could be inserted through an opening in the eye-piece 

 tube, the slit having one sliding jaw which could be adjusted as 

 indicated, and also to have the diffraction grating fixed in a small 

 plate, which can be inserted and slid into position through openings 

 in the eye-piece cap. In this way the eye-piece would be free for 

 its usual purpose entirely unspoiled, whilst it could be set up and 

 used as a micro-spectroscope at a moment's notice. 



I imagine that such a micro-spectroscope would be found useful 

 for a good many purposes, and do not know that a form having 

 the advantages mentioned has been suggested previously elsewhere. 

 If it has, no doubt it will be pointed out, and my apology then for 

 bringing the matter before you will be that so simple a form of 

 apparatus deserves to be more generally known. 



