O'Eeilly — On the Dates of Volcanic Eruptions. 417 



1360) is 29 wliicli is not a normal interval, but which corresponds 

 well with the interval between - 1889-6 and + 1860-2 = 29-4, and 

 which would indicate this as a maximum sun-spot year. This is 

 supported by the interval between + 1615-5 and 1360 = 255-5 quite as 

 nearly normal (11-1 x 23 = 255-3), and also corresponds with the 

 interval - 1889-6 - (- 1634) =255-6. There is no record of the 

 weather of this year in the works already referred to. 



The interval between this year and the preceding is twenty years, 

 which differs somewhat from the normal interval 22-2. 



The interval between + 1615-5 and 1340 is, however, 275-5, 

 which agrees fairly with the normal interval - 1889-6 - (+ 1615-5) = 

 274-1, and which would point to this year being taken as a maximum. 

 This is to a certain extent supported by the record given in Arago's 

 work, p. 269, for the year 1341 (probably the winter of 1340-41) : 

 '' Le froid de cet hiver fut si rude en Livonie que beaucoup de soldats 

 de I'armee des croises, eurent le nez, les doigts, ou les membres 

 geles." 



The interval between the third and the second eruption (1340 and 

 1188) is 152, which differs somewhat from the normal interval 155*4. 

 If, however, the interval be taken between - 1610-8 and 1188, the 

 result is 4228, which agrees well with the normal interval 421*8 

 (=11-1 X 38), and which would point to the year in question being 

 considered as a minimum sun-spot year. There is no record of the 

 weather for this year in the works already referred to. 



The interval between this and the previously mentioned eruption 

 year is thirty-seven years, which differs so from the normal interval 

 333, that it may be read 33-3 + 3*7, that is an interval of years 

 between a minimum and a maximum. This is supported by the interval 

 between + 1615-5 and 1151 = 464-5, which differs little from the 

 normal interval 466-2 = 11-1 x 42, so that, taking as a maximum sun- 

 spot year the date 1153, the agreement will be sufficient. 



The eruptions of Vesuvius and Etna are fairly well known, and 

 have been given with much detail in several well-known works which 

 will be found mentioned under the names of these volcanoes in the 

 articles of the " Encyclopaedia Britannica," from which I extract the 

 dates only, commencing with those relative to -^tna. 



[Table. 



