18 



SOLAR-DIURNAL VARIATION 



REGULAR SOLAR-DIURNAL VARIATION OP THE MAGNETIC DECLINATION, WINTER HALF YEAR. 



October, 



November, 



December, 



January, 



February, 



March, 



Oh. 



4 - 6 



8 10 Noon 14 16 

 Philadelphia mean time. 



18 20 22 24''- 



