OF THE MAGNETIC DECLINATION. 



11 



The month of May, in the year 1843, is indicated by the formula as the epoch 

 of tlie minimum amplitude. 



Regflak Solak-Diuknal Variation of the DECLiNATioif. 



^ 



14 



Philadelphia mean time. 



We now proceed to the discussion of the disturbances as far as they bear on the 

 decennial inequality, taking in also some collateral results. 



The total number of observations for changes of declination recorded and dis- 

 cussed amounts to 24,566 ; of these, 2357 were separated as disturbances differing 

 eight scale divisions or more from their respective normals, leaving 22,209 observa- 

 tions, from which the preceding results were deduced. There is one disturbed 

 observation in every 10.4 observations. 



The discussion of the disturbances divides itself into two parts, that of the 

 number and that of the amount of the larger deflections. 



