﻿ABSORPTION OF WATER VAPOR 



atmospheric water vapor, wavelength 0.814 

 << " •' " 0.896 



0.933 



0.945 



0.974 



" " '• 1 . 1 19 



1. 134 

 " " " " 1 . 1 72 



1.265 

 1 



unknown absorbent, 

 water vapor, 



i-45 1 

 1.469 

 2.049 



unknown absorbent, " 

 That the A line and the deepest portion of B are due to atmos- 

 pheric oxygen, has been shown by Egoroff. 1 A comparison of the 

 two curves in figure 1 of plate 1 shows the presence, however, of 

 considerable water vapor absorption in the " tail " of B. a was 

 found by Angstrom 2 to be due to water vapor. With the exception 

 of the lines at 1.265 /*> l -33 l P, an d 2.049^, probably the earliest evi- 

 dence of the origin of the others is in the work of Abney and Fest- 

 ing. 3 For the bands including par and those of shorter wavelengths, 

 the evidence rests most directly in their variations in intensity be- 

 tween moist and dry days. Paschen 4 finds W and $2 in the emission 

 spectrum of water vapor. Most of the bands, including 'F , are shown 

 in curves for the absorption of liquid water made by Abney and 

 Festing. 5 Moreover, the evidence for the water vapor bands (includ- 

 ing that at i-33/-<), §P ven m plate 1, figure 1, and plates iv and v. 

 should be conclusive of their origin. This does not necessarily 

 mean that the particular " nicks " in the curves are atmospheric ; 

 they may be due to some solar line superposed on the greater 

 atmospheric band. By far the greater portion of the absorption 

 must, however, be terrestrial. 



bouguer's fomula 



Before proceeding with the holographic observations in these 

 bands, the formula by which it is hoped to express these measures of 



1 N. Egoroff, Comptes rendus de I'Academie des sciences, 97, p. 555, 1883; 

 101, p. 1143, 1885. See also A. Cornu, Annales de chiinie et de physique (6) 

 7, pp. 5-105, 1886. 



2 A. Schellen, Die Spectra/analyse, vol. 2, p. 32. 



3 Capt. Abney and Col. Festing, Proceedings Royal Society of London. 35, 

 p. 80, 1883. 



4 F. Paschen, Annalen der Physik und Chemie, 52, p. 226, 1894. 



5 Abney and Festing, op. cit., p. 2,^. 



