i6 



SMITHSONIAN MISCELLANEOUS COLLECTIONS 



VOL. 66 



Table io. — Observations of the year 1914 (Continued) 



prior to and succeeding September 23, respectively, we find as fol- 

 lows : 



Table ii. — Comparison of results before and after Sept. 23, 1913 



Not only was this date critical with regard to solar-contrast and 

 solar-constant values, but a marked change in the distribution and 

 total amount of the water vapor in the atmosphere took place. The 

 values of precipitable water in the atmosphere determined by Fowle's 

 method were far above the normal until September 23, and from then 

 to the end of the period of observation generally about normal or a 

 little below. A similar change is indicated, but not in so great a 

 degree, by the observations with the wet and dry thermometers. The 

 temperature also fell at the same critical time. These changes are 

 shown by the following table (12) : 



Table 12. — Mean Mt. Wilson precipitable water, pressure of aqueous vapor 

 and dry bulb temperatures during observing periods 



