436 



SUMMABY OF OUKRENT RESEARCHES RELATING TO 



scope, without, however, being obliged to have a special Microscope 

 for the purpose. 



The apparatus is attached to the substage of the Microscope at O, 

 lying parallel with the anterior side of the stage. The light passing 

 through the slit Sp and the achromatic collimator C, is bent by the 

 white flint prisms P P at an angle of 90°, so as to pass in the direction 

 of the axis of the Microscope through an objective at 0, which may be 

 a low or high power as required. In front of the slit is a Praz- 

 mowski polarizing prism Po, which can be turned away on the frame 

 a k z when ordinary light is required to be used. Seleuites are intro- 

 duced at G. The prisms give a much wider and better spectrum than 

 a direct vision prism. 



The arrangement on the right consists of an Angstrom scale, the 

 image of which is projected by the lenses at Sk on the surface of one 

 of the prisms P, and is thus reflected into the field of the Microscope 

 in conjunction with the spectrum. As in the Zeiss Microspectroscope, 

 the wave-lengths are given direct. The milled heads S and Si serve 

 to move the apparatus from left to right, or from back to front, so as 

 to obtain an exact adjustment of the sj)ectrum, the proper focus being 

 obtained by the rack to the substage. The screws s and Sj also serve 

 to adjust the prisms accurately. 



Hartnack's Illuminating Apparatus for Monochromatic Light. 

 — The arrangement of prisms in the preceding apparatus is adapted 



Fig. 86. 



from that of Hartnack for obtaining monochromatic light. Two 

 white flint-glass prisms P i and P2 direct the rays passing through the 

 slit Sp and collimator lens C, so that they are projected on the stage 



