O'EiEiLLY — On the Dates of Volcanic Eniptions. 415 



The differences between the sun-spot dates and the corre- 

 sponding eruption dates are small, with the exception of that for 

 the year 1721. The remaining eruptions may be tabulated as 

 follows : — 



Erup- 







Inter- 



Estimates for 



tions. 



Date. 





vals. 



sunspot dates. 



6 



1580, August 11, .. 



.. = 1579-60 



163-60 



+ 1580? 



5 



1416, 



.. =1416 



106-93 



-1- 1416? 



4 



1311, January 25, 



.. = 1310-07 



48-07 



- 1310-07? 



3 



1262, 



.. =1262 



17 



+ 1262? 



2 



1245 



. . = 1245 





- 1245? 



1 



900, approximate. 









As in the previous cases, estimates are also made of the relation of 

 these to the sun-spot period. 



The interval between the seventh and the sixth eruption, 1624-66 

 and 1579'60, is 45-06, which approximates so closely to the normal 

 interval 44-4, that 1580 may be taken as a maximum year on that 

 account. We have, however, the interval -1889-6 and -1844 = 45*6, 

 which is also sufficiently close as a value. As there is no record of 

 the weather of the year in question, it remains doubtful under which 

 head to place it. 



The interval between the sixth and the fifth eruption (1579-6 

 - 1416) is 163*6, which differs somewhat from the normal interval 

 166'5, but which approximates to that between -1889-6 and -i- 1727*5 

 = 162-1. Taking the interval between -i- 1615-5 and the year in 

 question (1416), we have the interval 199-5 which practically re- 

 presents a normal interval, 199-8 = (11-1 x 18); so that for that 

 reason this year may be taken as a maximum sun-spot year. There is 

 no record of the nature of the weather for this year in the works 

 already referred to. 



The interval between the fifth and the fourth eruption (1416 - 

 1310"07) is 105-93, which is not a normal interval, but which cor- 

 responds fairly well with the interval between -1889-6 and -1784-8 = 

 104-8. Moreover the interval between - 1610-80 and 1310-07 is 

 300'73, which corresponds fairly well with the normal interval 



