For example, the number of stars whose spectra 

 could be photographed on a sufficient scale to 

 determine their radial motions would be trebled. 

 At present, the number of these objects is so re- 

 stricted that conclusions based on their study are 

 confined to a comparatively small region in space 

 closely surrounding the sun. 



FIG. 61. Driving Clock for zoo-inch Reflector. 



Quite as important would be the possibility of 

 photographing the spectra of the brighter stars 

 with high dispersion. For determinations of stel- 

 lar motions the spectrographs now in use are very 

 efficient. But in many other respects our present 

 position in stellar spectroscopy is closely analogous 



