268 CARNEGIE INSTITUTION OF WASHINGTON. 



All of the more important buildings on the mountain have been 

 painted during the year, including the Snow telescope building, the 

 two towers, and the two large domes. General repairs have been 

 carried on as usual in order to maintain the instruments in a high state 

 of efficiency. 



SUMMARY. 



The chief results of the year may be summarized as follows : 



Many dark hydrogen (Ha) floccuU, including "filaments," have 

 been identified with prominences. 



Stereograms of the flocculi, after eliminating certain false effects, are 

 useful in showing their relative levels. 



A new photographic map of the sun-spot spectrum, on a scale of 

 one centimeter to the angstrom, has been prepared for the region 

 X 6000 to X 6450. 



Observations of the polarization phenomena of Zeeman triplets in 

 spots near the sun's limb suggest that the fines of force spring from a 

 level below that of the region encircling the penumbra. 



Bipolar sun-spots in the northern or southern hemisphere, irrespec- 

 tive of latitude, are opposite in polai-ity to the bipolar spots of the cor- 

 responding hemisphere observed before the recent sun-spot minimum. 



The hydrogen vortices associated with sun-spots nevertheless retain 

 the direction of rotation which they showed before the minimum. 



Comparative studies of solar and vacuum-tube spectra hitherto 

 yield no reliable evidence of the existence of electric fields in sun-spots. 



The approximate inclination and period of the sun's magnetic axis, 

 as deduced from photographs covering 37 days, are as follows : 



P = 31^51 ±0''62 i = 5?2±0?5 1^ = 1914: June 25'^07±0''43 



The measurement of the separations of close pairs of fines in the 

 solar spectrum shows that such determinations are subject to syste- 

 matic errors. These errors depend upon the intensity of the con- 

 tinuous spectrum between the lines, the observer tending to make the 

 separation larger when the intensity between the fines is reduced below 

 that of the general background. The photographs taken with the 

 highest resolving power and showing the finest definition give the 

 smallest values for the separations. 



Measurements of close pairs of solar lines show systematic differences 

 between Rowland's values and those obtained at Mount Wilson, the 

 latter being the smaller. These differences depend on the amount of 

 the separations and are largest when the lines are very close to one 

 another. The Rowland errors cease to be systematic when the 

 separation is about 0.5 A. 



These errors appear to account fully for the apparent effect of 

 mutual influence among the Fraunhofer lines derived by Albrecht 

 from a comparison of results in Rowland's table with the International 



