THE ANNULAR SOLAR ECLIPSE OF MARCH 5, 1886. 91 



THE ANNULAR SOLAR ECUPSE OF MARCH 5, 1886. 



By George Davidson, U. S. Coast aud Geodetic Survey. 

 [Davidson Observatory.] 



This eclipse was only partial at San Francisco, where 

 four digits of the sun's diameter were obscured on the south- 

 east border. 



At San Francisco the clouds broke away about an hour 

 before the time of first contact, and the atmosphere became 

 moderately steady at that epoch. The sun's disc was 

 marked by three large groups of spots north of the equator, 

 and the details of these sj)ots became very sharply defined. 

 The bright facuhe about the western group were plainly 

 traced, and the rice-grain structure of the whole surface 

 was easily made out. 



The observations were made with the full aperture of the 

 Clark Equatorial of 6.4 inches diameter, using a Herschel 

 solar prism, and a power of about 170 diameters. 



The first contact took place at Ih. 16m. 58.5s. local sider- 

 ial time, and the second contact at 3h. 30m. 21.0s. The 

 second contact is a good observation, because it is easy to 

 watch the narrowing, dark segment of the moon, and also 

 because the observer can almost proportion the rate of the 

 rapid shortening of the two cusps. This observation is with- 

 in a fraction of a second. The observation of the first con- 

 tact is always more or less in doubt, because the dark limb 

 of the moon must have made its impression upon the limb 

 of the sun before the eye defects its approach; and this dark 

 segment is relatively long and narrow. When the border 

 of the sun is unsteady from the disturbance in the atmos- 

 phere, the difficulty is still further enhanced. Neverthe- 

 less, I consider the observation within a second or two. 



During the progress of the eclipse the images of the sun 



7— Bull, Cal. Acad. Sci. n, 5. Issued Aug. 31, 1886. 



