TERRESTRIAL MAGNETISM. 



Table 1 26. 



Secular Variation of Declination In the Form of a Function of the Time for a Number of Stations. 



More extended tables will be found in Apn. 7 of tlie United States Coast and Geodetic Survey Report for iSSS, from 

 which this table has been compded. 1 he variable m is reckoned from the epoch 1S50 and thus^ / — 1850. 



* Approximate expression. t East lonptiide. 



X Compiled from a series of observations extendin;; back to i;4i. The primary wave follows the sum of the con- 

 stant and first periodic term closely. The period seems to be about 470 years. In the expression for the secondary 

 wave n^t — 1 700. 

 Smithsonian Tables. 



