200 



OBSEKVATIONS OF THE TERRESTRIAL 



TABLE V. 

 Dip. Final Results. 



The dip being known, the intensity will be given by the formula 



sin (S - 0) = cos 0, 



(2) 



in which /3 is constant, and $ the measure of the force exerted 

 by the earth on the needle. This force, however, varies with the 

 temperature to which the needle is exposed ; and it is necessary 

 to determine the amount of this variation before we can know the 

 relative values of the terrestrial magnetic force at different stations. 



