296 THE SUN'S VISUAL ANGLE. 



sun is greater in winter than in summer that we are nearer the 

 sun in the cold season, than in the hot ! 



On more closely examining a result apparently so paradoxi- 

 cal, man discovered that the angle which subtracts the sun, as 

 seen from the earth, the visual angle which gives the sun's 

 apparent diameter, varies necessarily throughout the year. 

 Thus, the semi-diameter, or radius, which on the 24th of June 

 equals 15' 45", will, a month later, have increased one second 

 (15' 46") ; on the 2d of August will equal 15' 47" ; on the 2d 

 September, 15' 53", and so on. We put the exact measure- 

 ments before the reader in a tabulated form : 



LENGTH OF THE SUN'S RADIUS. 



On January 2 1, > i6'i6" 



February 25, . 16' 10" 



March 3 1, . i& i" 



April 30, . 15' 53" 



May 30, . ... I5'47 r 



June 24, minimum, 15' 45" 



On July 24, . . 1 5' 46" 



August 3, . 15' 47" 



September 2, . 15' 53" 



October 2, ; i6'i" 



November 6, .. . i6'io" 



December 2 1, maximum, i6'i7' 



We do not trouble the reader with the fractions of a second, 

 which indicate the quantity of the apparent increase of the 

 radius from the end of June to the end of December, and 

 its apparent decrease from the beginning of January to the 

 end of June. 



A glance at the above figures shows that the mean of the 

 apparent diameters, all measured at the moment of the sun's 

 passing the meridian, is about half a degree, or 30'; and 



