LIST OF ILLUSTRATIONS. xix 



IIG. PAGR 



114. The earth at an equinox 353 



115. Diagram to illustrate perihelion and a) ihftlum ..... 354 



116. Zones of the earth's surface 357 



117. Figure to show that apparent magnitude depends upon tlie 



visual angle 360 



118. Comparative sizes of the sun and the earth 363 



119. The great sun-spot of 1865 as it appeared on Oct. 15 . . 364 



120. Apparent paths of sun spots at different times of the year . 366 



121. The corona and solar prominences as seen during a total 



eclipse in 1851 . . . . ' 367 



122. Formation of the solar spectrum 369 



