AND OF TERRESTRIAL MAGNETISM 



259 



range of the figure. At first sight, one might have expected to find the maximum 

 on [mates in successive pulses decreasing after an exponential law. But two things 

 have to be remembered. First, the breadth of successive pulses increases as the height 

 diminishes, representing a distribution of energy over a greater and greater numl>er 

 of days ; and secondly, as has been already remarked, the true maxima do not 

 seemingly fall on exact days, so that the true maxima are not available. We should, 

 for instance, accepting the figures in Table IV., put the true maximum for the second 

 associated pulse between days 54 and 55, and the numerical value corresponding 

 would thus naturally be in excess of 454, the value found for day 54. A similar 

 remark applies to the other associated pulses, so that the ratios given above are at 

 best only approximations to the truth. 



13. Evidence that the results of 8 to 12 are not confined to the period 1906 to 

 1911, nor due to any peculiarity in international " character " data, was derived from 

 a study of data for 1890 to 1900. The results of this investigation are summarised in 

 Table V. They were derived from days associated with disturbed days. Only the 



TABLE V. Primary Disturbance Pulse and Associated Pulses, Years 1890 to 1900. 



(Unit = O'OOl " Character" Unit.) 



first previous pulse was considered, but the investigation extended to the fourth 

 associated subsequent pulse. The entries in the table are the excesses of the mean 

 "character" figures for the days stated over the normal figure 0'G97 derived from 

 all days of the 11 years. To avoid decimals the unit employed is O'OOl of the 

 " character " unit, as in Table IV. The associated disturl>ed day had a " character " 

 figure in excess of the normal, except in the one case in which a negative sign appears 

 in the table. The representative disturbed day is descril>ed as day 0, as in Table IV. 

 The maximum for each pulse is in heavy type. 



Uncertainties arising from variations in the normal " character " figure appropriate 



2 L 2 



