O'Reilly — On the Dates of Volcanic Ernjjtions. 



427 



No. 



Date. 



Interval. 



Wolf's List 

 Numbers. 



DifiFerence. 



66 



1799 January . 



. = 1798-08 





- 1798-5 



0-42 



67 



1804 July 26 . 



. = 1803-57 



— 



+ 1804 



0-43 



68 



1805 Aug. 12 . 



. = 1804-63 



— 



— 



— 



69 



1806 



. = 1806 



— 



— 







70 



1809 Sept. 4 . 



. = 1808-67 



— 



— 



— 



71 



1812) .. 



. (= 1812 



— 



- 1810-5 



1-50 





1813} .. 



. = 1813 



— 



— 









1814) .. 



. (= 1814 



— 



_ 



— 



72 



1816 Aug. 7 . 



. = 1815-60 



— 



— 



. — . 



73 



1817 Dec. 22 . 



. = 1816-90 



— 



+ 1816-1 



0-80 



74 



1S18\ .. 



. / = 1818 



— 



— 



— 





1819/ .. 



. - 1819 



— 



— 



— 





1820 ( .. 



. ) = 1820 



— 













1821 ; . . 



. ' = 1821 



— 



— 







75 



1822 Feb. 23 . 



. = 1821-15 



— 



- 1823-20 



2-05 



76 



1828^ .. 

 1829 



. f= 1828 



— 



— 



— 





. = 1829 



• — 



+ 1829-5 



0-50 





1830 ... 



1831 f .. 



. = 1830 

 . ] = 1831 



— 



— 









— 













1832 1 .. 



. ! = 1832 



— 



— 









1833J .. 



. L= 1833 



— 



— 







77 



1834 Aug. 



. = 1833-59 



— 



-1833-8 



0-21 



78 



1838 Mar. 6 . 



. =1837-17 



— 



+ 1837-2 



0.03 



79 



1839 Jan. 



. = 1838-01 



— 



— 







80 



1841 



. = 1841 



— 



— 







81 



1845 April 22 . 



. = 1844-31 



— 



- 1844 



0-31 



82 



1847 Nov. 13 . 



. = 1846-87 



— 



— 







83 



1848 June 



. = 1847-42 



— 



— 







84 



1849 Dec. 



. = 1848-92 



— 



+ 1848-6 



0-32 



85 



1850 Feb. 6 . 



. =1849-17 



— 



— 







86 



1855 Jan. 



. = 1854-01 



— 



— 







87 



1858 May 21 . 



. = 1857-42 



— 



- 1856-2 



1-22 



88 



1860 



. = 1860 



— 



— 



— 



89 



1861 Dec. 8 . 



. =1860-92 



— 



+ 1860-2 



0-72 



90 



1867 Oct. 



. = 1866-75 



— 



- 1867-2 



0-45 



91 



1871-2 .. 



. = 1871-2 



— 



+ 1870-7 



0-30 



The dates in the list prior to 1631 may be treated in the same 

 manner as were those o£ Etna and the Iceland volcanoes, that is, an 

 estimation can be made as how far these dates correspond with sun- 

 spot years of maxima or minima. 



In the present case these estimations give figures so close as to 

 compare favourably with those arrived at in cases of the previously 

 considered volcanoes. 



Thus the eruption year 1500 gives with the sun-spot minimum year 

 -1610'8 an interval of 110-8 years, which practically agrees with the 

 normal interval 111 = (= ll'l x 10). Moreover the interval between 



2 H 2 



