260 CARNEGIE INSTITUTION OF WASHINGTON. 



is 0.001 A, and that we are here concerned with quantities of the second 

 order. 



The reductions have been kept up to date by Miss Wolfe and Miss 

 West under the direction of Mr. Seares, but of course no definitive 

 values can be given until all of the measurements and the least-squares 

 solutions have been completed. From present indications the incUna- 

 tion and period will not differ greatly from 5° and 30 days (synodic), 

 respectively. 



The pubhcation of the complete results for intensity of field for the 

 25 lines mentioned above has been greatly delayed, owing to difficul- 

 ties in measuring some of the lines with the Koch machine. These 

 measurements are necessary in order to determine personal equation 

 and the possible effect on the displacement of the width and character 

 of the line. The difficulties are mainly due to the narrowness of the 

 strips of spectra, which causes the silver grain to play a conspicuous 

 part in the records. It is expected, however, that satisfactory results 

 will be obtained by a slight modification of the method. 



THE STARK EFFECT. 



If the general electric field of the sun is sufficiently intense to give 

 an appreciable Stark effect at the hydrogen level, the edges of the 

 hydrogen lines should be plane polarized and thus capable of being cut 

 off with a Nicol prism. An investigation has been made by Mr. Hale 

 and Mr. Babcock to test this question. Photographs of the hydrogen 

 lines near the sun's limb were taken with the 75-foot spectrograph, 

 using a Nicol prism and compound half-wave plate above the slit. 

 Measurement of Ha and H^ on curves made with the Koch micro- 

 photometer showed no appreciable difference in width for the odd and 

 even strips. From Stark's results we may therefore conclude that the 

 intensity of the sun's electric field does not exceed 200 volts per centi- 

 meter at the hydrogen level. 



In order to extend this investigation to sun-spots, it is necessary to 

 determine the Stark effect for the lines of iron, chromium, titanium, 

 and other elements which lie at a comparativel}^ low level in the solar 

 atmosphere. As stated elsewhere, complete laboratory equipment 

 has been provided for this purpose, and it is hoped that both the solar 

 and laboratory phases of this research, which have been held back by 

 the pressure of other work, may soon be in full progress. 



PRESSURE AND MOTION IN THE SOLAR ATMOSPHERE. 



Mr. St. John's investigations bearing upon pressure and motion 

 at different levels in the solar atmosphere are still in progress. The 

 results on the spots of the new cycle confirm the observation of the out- 

 flow of the low-lying vapors and the inflow of those at the highest 

 levels. The long plates (90 cm.) allow a range of 600 a to be cov- 

 ered with the 75-foot spectrograph and permit overlapping series to 



