AND OF TERRESTRIAL MAGNETISM. 



251 



as the period seems in excess of 27 days. As the expected effect appeared likely to 

 be small, it seemed best to utilise the data from the longer period of years 1890 to 

 1900. Calculations in that case had previously extended to day n + 35, and they 

 were now extended to day n + 60. " Character" figures were assigned to the earlier 

 days of 1901, so as to utilise all the 660 selected disturbed days of the 11 years. 

 The mean "character" figure from all days of the 11 years was 070. The mean 

 " character" figures up to day n + 35 are given in S.M. (Table XL, p. 101) ; those for 

 days 7i + 36 to n + 60 are given in Table II. 



TABLE II. Mean " Character" Figures for Days n + 36 to n + 60, n being the 

 Eepresentative Disturbed Day of the 11 Years 1890 to 1900. 



As shown in S.M. (Table XI.), the " character" figure lay between 0'61 and 0'66 

 from day n + 5 to day n + 24, and exceeded 070 only from days n 2 to n+3, and 

 days ?i + 25 to n+31. There is thus clear evidence in Table II. of a pulse from day 

 n + 52 to day n + 58, or possibly n+ 59. The figures for days n + 54 and n + 55 distinctly 

 overtop their neighbours, that for day n + 55 being slightly the higher. 



8. Reasoning in the same way as before, we should now expect an excess in the 

 " character" figures for days n + 79 to n + 84, and so on. It will probably have been 

 realised ere this that carrying the investigation up to day n+60 entailed exceedingly 

 heavy arithmetical labour, and, as the time at my disposal was limited, it was 

 important to economise effort. It was anticipated that the successive pulses would 

 diminish rapidly in .magnitude, and that they would spread themselves over an 

 increasing number of days, so that the distinction from neighbouring days would be 

 more and more difficult to establish. Further, there is the possibility that normal 

 conditions at the time, which includes days which follow the selected disturl>ed days 

 after a long interval, may differ sensibly from normal conditions answering to the 

 selected days themselves. 



2 K 2 



