Smithsonian Report. 1941. — Adams 



PLATE 1 



Ked 



FIELD OF NGC 6553. 



Photographed bv Baade in blue and in red light. The exposure times were so chosen that an unobscured 

 field of normal color would have appeared similar on the two photographs. Clouds of cosmic dust be- 

 tween us and the stars scatter and absorb the blue light much more than the red. 



