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ANNUAL REPORT SMITHSONIAN INSTITUTION, 19 31 



infra-red solar spectrum region. He finds that our old bolometric 

 work of 1000 deserved a good word as to the accuracy of the wave 

 lengths and as to the general reality of the lines found and that our 

 new work added to it some really useful detail. 



Many of the infra-red spectrum lines are now identified by investi- 

 gators as due to specific elements in the gases of the sun, others to 

 vapors in the earth's atmosphere. There were two mystery bands in 

 the spectrum called wi and w. of wave length about 2.0 microns, 

 which long puzzled us because we knew they were atmospheric but 



