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Proceedings of the Royal Irish Academy. 



inference that the correspondence between volcanic eruptions and 

 minima sun-spot years, is much closer than as regards maxima sun- 

 spot years, and seemingly more frequent. In order to complete the 

 list, estimations will be given for the years mentioned in the list, 

 prior to 1610. 



Date. 



Interval. 



Date. 



Interval. 



1607 





1565-85 







4 





29-52 



1603 



24 



1536-33 





1579 





1535-15 







13-15 



1447 



88-15 



Allowing a usual interval between a minimum and a maximum 

 3 to 4 years, the year 1607 may be taken as representing 

 a maximum sun-spot year ; that is supported to some extent by the 

 record of the winter of that year, as given in Arago's work already 

 cited: "L'hiver de 1608, f ut longtemps appele /^ grand hiver. Le 

 froid sevit presque sans intermittance depuis le 20 Decembre 1607, 

 jusqu'^ vers le milieu de Mars 1608 en France, en Angieterre, en 

 Hollande, en AUemagne, en Italic. Les historiens abondent en details 

 sur les effets de la gelee. Dans la partrie septentrionale de I'Europe, 

 tousles fleuves furent pris. La plupart des jeunes arbres perirent, le 

 froid gela une partie des vignes jusqu'4 la racine. L' Angieterre vit 

 presque tout son betail detruit. 



" A Londres la Tamise etait gelee au point que des chariots charges 

 la traverserent. 



" II tomba a Padoue une immense quantite de neige." 



The year 1603 may have been a minimum. The weather of the 

 year is mentioned in Arago as follows : "Get hiver fut encore tres 

 rigoureux dans le midi de la Prance. Des charrettes passerent sur 

 le Phone congele " (Arago, op. cit). 



The year 1579 makes with the year 1610-8, an interval of 31-8 

 years, which differs from the normal interval by 33-3-31-8 = 1-5, 

 an approximation sufficient to allow its being considered as a minimum 

 sun-spot year. There is no record of the weather for this year in the 

 works already cited. 



The year 1565-85, shows with the year - 1610-8, an interval of 

 44*95 years, which compares well with the normal interval of 44-4, 

 and would allow of its being taken as a minimum year of sun-spots. 



