20 



SMITHSONIAN MISCELLANEOUS COLLECTIONS VOL. 68 



TRANSPARENCY FROM 1.2 TO 9.0 \i 



In the upper portion of figure 6 will be seen a curve drawn from 

 a hologram showing the distribution of energy in the spectrum of the 

 lamp of Nernst glowers after the passage of its radiation through the 

 air, carbon dioxide and aqueous vapor in the path through the 

 spectroscope alone. 



Z.OjU 3.0/u 



%0m 



QDm 



Fig. 6. — a, Bologram Nernst lamp, 60° rock-salt spectrum ; a, ditto corrected 

 for slit and bolometer widths ; ppt. H2O, o.oi cm. ; b, ditto, ppt. H2O, o.i cm. ; 

 c, black-body curve, 2,200° K. 



To see whether any of the energy at the longer wave-lengths was 

 due to energy scattered from the shorter wave-lengths, several 

 holograms were made with a quartz plate I cm. thick inserted be- 

 tween the lamp and the slit. No appreciable deflection was observed 

 beyond 4 fi, where quartz becomes opaque. Hence there is no appre- 

 ciable energy at the deviations corresponding to wave-lengths greater 

 than 4. fx contributed by radiation of shorter wave-lengths transmissi- 

 ble by quartz. 



