PHYSICS: BRINSMADE AND KEMBLE 
421 
In this manner a curve was obtained, showing the transmission of the 
tube relative to an air path of equal length. The absorption in the gas 
was computed by comparing the transmission curve for the tube when 
evacuated with that when filled with the gas under investigation. From 
two to six complete sets of observations were taken at each spectrometer 
setting. 
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FIG. 1. FIG. FIG. 3. 
. HCI iHarrnoriic ; ; 
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Carbon Monoxide. — According to Burmeister^ the principal infra-red 
absorption band of CO is a doublet whose maxima are at 4.60 and 4.72 
/X. The center of the harmonic should accordingly be at 2.33 fx. It 
should be a doublet with one fourth the wavelength difference between 
the maxima that is observed in the fundamental. Figure 1 shows the 
