8 POPULAR SCIENCE MONTHLY. 



first slit, an image of the prominence will be recorded upon the plate. 

 The principle of the instrument thus lies in photographing the solar 



H K 



Fig. 1. — // and K Links on the Disk, in the Chromosphere, and in a Prominence (a). 



flame through a narrow slit, from which all light is excluded except that 

 which is characteristic of the prominence itself. 



