Investigations with the JEchelette Grating. 



899 



practically of the same height, and the minimum between 

 them has an intensity of only about 1/3 that of the maxima i 



in other words, it is very much deeper than when observed 

 with a rock-salt prism. The slit width w r as only half a milli- 

 metre, and the width of the bolometer strip was the same. 

 This type of curve was obtained with all of the gratings 

 The maximum at 13, figured by Coblentz, who worked with 

 a single reflexion only, did not appear in our work, as it was 

 lost by the threefold reflexion which we employed. The 

 curve obtained with the radiations of CO from the Bunsen 

 flame is shown in fig. 2. There is distinct resolution of the 

 band into a double band in the case of every curve obtained. 

 In addition to the strong band at 4' 3 there are weaker 

 maxima to the right and left. The curve figured was 

 obtained w T ith grating No. 8. 



