16 



SOLAR DIURNAL VARIATION 



The summer months comprise April to September, inclusive 

 The winter October to May, 



One scale division equals 0.0000365 parts of the force. 

 Increasing numbers denote decrease of force. 



Subtracting each value from its respective monthly mean value and converting 

 these differences into parts of the force, we obtain the numbers of Table II ; a + 

 sign indicates a greater force than the normal value, a sign a smaller one. The 

 first three decimals are placed at the head of the table. 



