^~~^ 



Fig. I . 



-Inner room containing radiometer R, spectrometer and prism P, exhaust pump G, lamps and scale L, and 

 telescope T. C is the holder for the absorption cell. S is the shutter, H the Nernst lamp-heater. 



Fig. 1 A.— Large spectrometer with Nernst heater, /* , to the right, and radiometer, r, to the left. The gas-cell holde 

 and glass cells are shown at 9; Ceissler pump in the rear. Photograph taken through doorway of inner room. 



