360 



SUMMARY OF CURRENT RESEARCHES RELATING TO 



screw H. This upper part consists of a flat semicylinclrical box B, and 

 is accurately adjusted to the observation telescope C and scale-tube D. 

 The box contains the Thorp transparent grating. The telescope can by 



Fig. 72. 



rotation of the screw E be brought over the spectrum. The four slides 

 G- on the telescope ocular serve for the delimitation of a small rect- 

 angular field for photometric comparison. The scale-tube can be accu- 

 rately applied to the spectrum by means of the screw F. 



