NIPHER MAGNETIC OBSERVATIONS IN MISSOURI, 1878. 93' 



Magnetic Moment during Sumtner of 1818. 



Taking the mean of the cokimn headed " Days," beginning 

 with July 7th (but rejecting the observations of Aug. 14th), it is 

 found to be 26, corresponding to Aug. 2d. 

 Assuming 



log m ■=z log W(j _ ad , 

 where 



d =: number of days, estimated from Aug. 2d, 



log m^ z= value of log m on Aug. 2d rr: 9.87323. 



a = the change in log fn per day. 



The observations give 20 equations of condition of the form 



e = log fn^^ _ log m _ ad , 



from which, by the method of least squares, we find 



a = _ 0.C0012 , 

 and hence 



log m = 9.87323 -(- 0.00012 d. 



The negative value of a and an inspection of the values of log. 

 m, in the pi-evious table, shows that further reduction would be 

 unprofitable. It will be deferred until next year. 



