MAGNETIC DISTUEBANCES AND AURORA. 



195 



varied with the season, and 1903 was decidedly more disturbed than 1902, so that nothing like an exact 

 standard of disturbance could well be maintained. 

 The results were as follows : 



TABLE LXXIII. 



On a good many of the occasions when the curves were quiet the aurora is described as faint, or very 

 faint, but this was not always the case. Thus, on May 31, 1903, a species of corona is described as visible 

 at 4 p.m. (see Plate 13, "Physical Observations") having " intensity bright as it rose to the zenith." The 

 magnetic curves were, however, unusually quiet at 4 p.m. and for some time afterwards. There was a 

 minor disturbance about 3.30 p.m., but it had subsided before 4 p.m. 



113. The second attempt referred to above consisted in examining individual magnetic curves more 

 minutely, to see whether anything special happened at the precise times when aurora was noted. 



A judgment was passed as to whether a correspondence existed. Cases which, so to speak, seemed 

 worth sending to a jury, were adjudicated as to whether the correspondence were " possible," " probable," 

 or " apparent." These terms may be interpreted as follows : 



" Possible " correspondence means that whilst the average man would probably decide against a true 

 correspondence, he would experience more or less hesitation in doing so. In the case of " probable " 

 correspondence the verdict would naturally be favourable, but again with hesitation. In the case of 

 " apparent " correspondence there could be little doubt that a marked magnetic movement occurred during 

 the observed aurora. 



The decisions reached were as follows, the numbers denoting days on some of which more than one 

 correspondence was considered : 



1 1 4. The cases of apparent correspondence are included in the following list. Details of the magnetic 

 disturbances are given in parallel with the description of the auroras as given by Mr. BERNACCHI. 

 Directions are geographical unless the contrary is explicitly stated. 



2 C 2 



