24 



SOLAR DIURNAL VARIATION 



The diurnal range is greater about the time of the equinoxes than at any other 

 time, and in general less in winter and greater in summer. The afternoon minimum 

 disappears about the time of the equinoxes, and is best marked about the solstices ; 

 the early night minimum only disappears about the time of the winter solstice. 



Solar-Diurnal Variation of the Total Force. The combination of the component 

 values of and - to form the corresponding values of the total force is effected 



by the formula 



<p j. ^L 



the result being expressed in parts of the force. A + sign indicates an augmenta- 

 tion of the force, a sign a diminution. 



1 About 3\ A. M. ; minimum not distinctly marked. 



