ANI> OF TKKi;l-:sTi;lAL MAGNKTISM 



257 



symmetry. This has been done in Table IV., the entries in which represent the 

 differences of corresponding D and Q results in Table III. To save decimals, the 

 results are expressed in terms of O'OOl "character" unit as unit. As day 

 i.e., what is called day n in Table III. is neither previous nor subsequent, but 

 fundamental for both previous and subsequent days, it appears in both the first and 

 second lines of Table IV. The entry 1186 ascribed to it represents of course 

 ( 1 '321 -0*135) x 1000. The algebraic sign when omitted is plus. The "character" 

 figure for the associated disturbed day was invariably the larger, except for the third 

 days before and after (he selected days. 



TABLE IV. Differences Disturbed less Quiet Associated Days (Unit = O'OOl of 



"Character "Unit). 



The accordance between the results for the previous and the subsequent days 

 1, 2, and 3 in Table IV. is quite extraordinarily close. In other words, the primary 

 pulse obtained by taking the excess of " character " figures for selected disturbed 

 and adjacent days over the corresponding figures for selected quiet and adjacent days 

 is almost perfectly symmetrical as between time previous and time subsequent. We 

 cannot hope to see equal symmetry in the associated pulses, whose form is necessarily 

 more dependent on accident, but there is at least no marked a-symmetry in the second 

 and third associated pulses. If curves were drawn to represent these, they would 

 not be markedly steeper on one side of the maximum than the other. This suggests 

 adding the two sets of results, as has been done in the last line of Table IV., and 

 applying the sums to the evaluation of the period. The most orthodox way probably 

 would be to fit an algebraic curve to each of the successive sets of figures, and 

 calculate the abscissa of its maximum ordinate. But as there is nothing to guide one 

 as to what the theoretical shape of such a curve should be, rougher methods may not 



VOL. CCXIII. A. 2 L 



