Table X.— Annual Secular Change in the Magnetic Declination, on the average of fifty-three years antecedent to 
January 1840, taken to the nearest half-minute. The sign + in this table implies that the secular change in the period 
referred to was increasing westerly, or decreasing easterly Declination ; and the sign — implies the change to have been 
decreasing westerly, or increasing easterly Declination. 
LINES OF MAGNETIC DECLINATION IN THE ATLANTIC 
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