NO. 8 



WATER-VAPOR TRANSPARENCY FOWLE 



41 



deflections with the iodine screen in, after subtracting the field Hght, 

 were of course very small for wave-lengths less than 9 fx partly be- 

 cause of the opaqueness of the iodine itself and partly because of the 

 great water- vapor band preceding 9 /^. 



SOLAR OBSERVATIONS 



Returning now to the observations on the sun, the following 

 energy curves were made with the assistance of Dr. Abbot and 

 Mr. Aldrich: 



Bgm.s. I and V. Solar spectrum made with apparatus prepared 

 for North Carolina solar-constant work. Bgm. I taken at hour angle 



Fig. 13. — Bolograms of solar 15° rock-salt spectrum. Wave-lengths are at the 



top of the plate. 



Bgm. II, air mass 1.5, ppt. H2O 0.7 cm. 

 Bgm. IV, air mass 2.1, ppt. H2O i.i cm. 

 Bgm. VI, air mass 3.0. ppt. H2O 2.0 cm. 

 Bgm. VII, air mass 4.1, ppt. H2O 3.0 cm. 



i^ 42™ W., air-mass 1.3, for purpose of determining by the depths of 

 the water-vapor bands p and (f> the amount of aqueous vapor in the 

 path of the sun's rays through the atmosphere. These bands have 

 been calibrated (see Astrophysical Journal 35, p. 149, 1912) against 

 known amounts of water vapor. 



Bgm. II. Solar spectrum made with spectroscope as used in 

 the tube work, but with the iodine screen in front of slit. H. A. 



