F. H. JBigelow — Further Study of the Solar Corona. 355 



ured ; p is the angular distance from the pole on the disk ; A 

 and B the interior angles of the triangle at the respective poles, 

 and g the required angular distance of the coronal pole from 

 the disk plane. 



Now investigate the heliographic latitude over which these 

 coronal streamers appear to terminate as definite lines. By 

 many computations it is found that the r for the extreme 

 points measured is equivalent to the logr' = - 39800, of lines 

 which leave the sun at polar distance d' = 34°. 



8zr sin 2 $ , ,„..._,. 



, where r — 1 at the surface: hence JN = 2-620. 



N = 



Then, sin 2 = 



N.3 r' 



and 6 = 62° 10'. 



The corresponding equatorial distance is 90° — 62° 10' = 27° 50', 

 which is in the midst of the zone of the sun spots at the mini- 

 mum of the period. 



The heliographic latitude and longitude of the north and 

 the south coronal poles, as seen on July 29, 1878, are obtained 

 as follows. 



5 



,WTU SP*U. 



/V<rrTdjL "Pa-U. 



Location of the coronal poles for July 29, 1878. 



K Poles of the ecliptic. 

 S Poles of the sun's axis. 

 E Poles of the plane of the equator. 

 C Poles of the corona. 

 D The center of the disk. 



KP The plane through the poles of the ecliptic perpendicular to the radius 

 vector to the earth. 



M The projection of poles of the corona on the disk. 



N " " " sun 



P " " " equator " 



O The direction of the ascending node at 74° longitude. 



