THE BLOOD. ]<;; 



the microscope the object-glass required and place the object whose 

 spectrum is to be viewed on the stage. Illuminate with stage mirror 

 if transparent. Remove A and open the slit by means of the milled 

 head H at right angles to /?, D. When the slit is sufficiently open 

 the rest of the apparatus acts like an ordinary eyepiece, and any 

 object can be focused in the usual way. Having focused the object, 



Fig. 57. Sorby-Browning Microspectroscope. 



replace A and gradually close the slit till a good spectrum is 

 obtained. The spectrum will be much improved by throwing the 

 object a little out of focus. Every part of the spectrum differs a 

 little from adjacent parts in refrangibility, and delicate bands or 

 lines can only be brought out by accurately focusing their own parts 

 of the spectrum. This can be done by the milled head B. When 

 spectra of very small objects are viewed, powers of l / 2 inch to % 

 may be employed. 



These bands represent the light absorbed by the colored medium. 



13 



