18 



SOLAR-DIURNAL VARIATION 



Regular Solar-Diurnal Variation of the Magnetic Declination, Winter half Year. 



October, 



November, 



December, 



January, 



February, 



March, 



3' 



i 



1 



o 

 -l 



-2' 



Oh. 



8 10 Noon 14 16 18 20 22 241' 

 Philadelphia mean time. 



