MAGNETIC OBSERVATIONS. 



55 



The Magnetic Moment of the Magnet C 32 was computed as follows : Observations 

 of deflection were always taken at two different distances, viz., at 2.0 feet and at 



2.5 feet. In general, the two values of - thus obtained differed slightly from each 



other, and the mean of the two was assumed to be correct. This mean was com- 

 bined with the value of mX, obtained from a set of vibrations observed on the same 

 day, and thus m was determined. In no case was more than one set of observa- 

 tions of deflections taken on any single day, but in a few instances several sets of 

 observations of vibrations were made. Under such circumstances, the mean of all 



the observed values of mX was combined with the mean of the two values of "- , 



X 

 and thus a single value of m was deduced. 



Let 



m r = observed value of the magnetic moment at the temperature t. 

 m = value of m T after being multiplied by [ 1 -(- (r 75.8) q ], or, in other words, 



after being reduced to the temperature 75.8 Fah. 

 n> = mean of all the observed values of m. 

 a = daily decrease in the value of log. m, expressed in units of the fifth decimal 



place. 

 d = time in days at which m is taken; d being counted from March 7th, 1866. 



The following table contains all the observed values of log. m r , together with the 

 computation from them of the final values of the same quantity. The column 

 headed "days" gives the time in days counted from October 24th, 1865. 



