410 Proceedings of the Royal Irish Academy. 



winter corresponding to the year in question. Poey, in his Paper of 

 Compt. Eend., 1873 (vol. Ixsvii., p. 1222), points out a coincidence of 

 a series of severe winters with maxima of sun-spot periods, and if the 

 records of the seasons, such as they may be found in various works be 

 consulted, it will be found that this coincidence frequently presents 

 itself. Now it is mentioned in Arago's works (vol. 5, " Q5uvres 

 completes"), "Sur I'etat Thermo metrique du Globe Terrestre," p. 418, 

 that the summer of the year 1578 was remarkably warm in France 

 and Belgium. " On ressentit en Belgique des chaleurs excessives 

 La secheresse dura depuis Mai jusq'en Septembre (Quetelet). On 

 vendangea k Dijon le 22 de ce Mois " ; and for the year 1610 (a 

 minimum sun-spot year), he has the record : " L'ete fut ex- 

 cessivement chaud et sec, et il y eut grande abondance de vin (Short). 

 Ou vendangea a Dijon le 20 Septembre." 



I find, however, no mention as to there having been a severe 

 winter this year. The presumption, therefore, so far as this character 

 is concerned, is that the year 1578, either was a minimum sun-spot 

 year, or near to it in date. 



The eleventh eruption of 1554, end of May (= 1553-42) shows 

 an interval of 24 from that of 1578, or more correctly -24*6, that is in 

 excess of the normal interval, 22-2 by 2*4 years. If it be compared 

 with the minimum of 1610"8, the interval comes out 57"4 years, 

 that is in excess of the normal interval by 2*2 years. The winter 

 of the year 1554 is mentioned in our annals as follows: — "This 

 year was a very sad winter, especially from the 21st December to 

 the end of the following spring, either perpetual hail, rain, or 

 tempest." 



If it be compared with the year 1597, which may be taken as a 

 minimum year, the interval is 42-6, showing difference from the 

 normal time of 1*8 year. The eruption took place, therefore, within 

 about two years of the sun-spot minimum, which probably fell in 

 1552, the winter of which 1552-3 was a memorable one in the 

 Dutch records for its severity. (See Arago's work cited, for that 

 winter.) 



The tenth eruption, that of 1510, 25th July (= 1509-59), shows^n 

 interval from 1610-8 of 101-2 years, comparing fairly well with tne 

 interval between 1889-6 and 1789 = 100-6 years. Furthermore, the 

 interval between the 11th and 10th eruption is 1554 - 1510 = 44 years, 

 practically the quadruple sun-spot period (44*4). As regards the 

 character of the winter, the following is the passage in regard to it in 

 Arago's work already cited (vol. 5, p. 274) : — " 1510-1511. Get hiver 



