298 



light tight. Al A an attachment is arranged to hold a ground glass for fo 

 ing purposes, and a common camera plate holder for making tin- exposuri 



The camera tube is mounted on a common prism spectrometer in place of 

 the telescope as shown in Fig 2. The collimator slit, prism, and light source 

 to he studied are adjusted in the usual way. When all adjustments, together 



Fi?. 2. 



with focusing the objective lense of the camera, have been made, a clearly 

 defined spectrum image, including the Fraunhofer lines, may be seen upon the 

 ground glass. In the usual procedure a plate holder containing an unexposed 

 plate may be substituted for the ground glass and the exposure made. 



The instrument constructed in our laboratory has proven to be very 

 successful for student work. 



