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DK. CHARLES CHREE: SOME PHENOMENA OF 



which are quiet according to the Astronomer Royal's standard, while " 2 " is limited 

 to days which are so highly disturbed as to merit inclusion in the list of those the 

 curves for which are reproduced in the annual Greenwich volume. The lists for 

 Greenwich and Kew are got out independently. The figures suggest that the 

 standard has varied at one at least of the two observatories, but the following 

 results from the three most recent complete years give totals in truly remarkable 

 agreement : 



The three years were in no way specially disturbed, rather the contrary, and yet 

 over 60 per cent, of the days were classified as days of greater or less disturbance. 



No day, it is true, is classified as " " if any part of it is highly disturbed, while 

 many days classified as " 1 " were doubtless of standard " " during part of the 

 24 hours. On the other hand, quiet and disturbed days have rather a tendency to 

 occur in groups, so that a disturbed day is more likely to have its adjacent days 

 disturbed than the above figures would suggest. This is a feature which the 

 international lists bring out in a striking fashion. During the three years the number 

 of days classed as "2" was 29 at both Kew and Greenwich. Each list included 

 19 days common to the other list and 10 special to itself. The days immediately 

 preceding and succeeding these days were classified as follows : 



Thus in no single case was a highly disturbed day followed by a really quiet one, 

 and the number of instances in which it was preceded by a quiet day is much less 

 than would have been anticipated from a consideration of the relative frequency of 

 quiet and disturbed days. 



