406 Proceedings of the Royal Irish Academy. 



expression to his faith in the sun-spot period influence, and which merits 

 attention at present (1899) in view of the disastrous droughts which 

 have reigned in Australia for some years, acd which are foretold in 

 the forecast table of this work for the years 1898-99, 1900-1-2-3 

 ("with mitigation in 1901"). In Nature, toI. xxxvi., p. 229, 

 appeared an article on " The 11th year Periodical Fluctuation of the 

 Carnatic Eainfall," which bears to some extent on the question. 



Other Papers might be cited, but enough is here given to show that 

 the connection has been observed and taken into consideration by more 

 than one or two observers. As to the relation which may exist between 

 volcanic eruptions and winds and seasons, I would refer in that con- 

 nection to my address to the Eoyal Greological Society of Ireland, read 

 the 16th !N^ovember, 1885,^ wherein I insisted on the importance of 

 the vast volumes of gases and very fine dust material projected into 

 the upper atmosphere by many of the active volcanoes. These gases 

 and dust tend, on the one hand, to modify the upper currents of the air 

 (and in so far to influence the winds), and on the other, to modify the 

 quantity of heat absorbed by the atmosphere by its greater or less 

 volume, and so become a factor as regards rain seasons, &c., since it 

 has been shown by Aitken that rain is intimately connected with the 

 quantity of dust present in the air. The events which accompanied 

 and followed the eruption of Krakatoa fully illustrated these ideas, 

 and on a scale of the grandest magnitude. (It is worth while men- 

 tioning here that the sun-spot period was maximum in 1 883*8, the date 

 of the eruption having been 26th, 27th August, 1883 (= 1882-63).) 



Why so little attention has been given by geologists to the sun- 

 spot period in relation to the periodicity of phenomena occurring at 

 the surface of the earth, may be explained by the relatively recent 

 date of the publishing of "Wolf's work, and by the shortness of the time 

 covered by his list, which does not go farther back than 1610. There 

 is also the want of complete lists of eruptions, earthquakes, auroras, 

 &c., with wliich to institute a comparison in the different cases which 

 may present themselves for consideration. The tables published by 

 Kluge and by Poey, only give totals of hurricanes, eruptions, or 

 earthquakes for given sets of years, and could not therefore be 

 checked or controlled, except by comparison with the lists of Mallet, 

 and Perrey, and Palb, a work most onerous and tedious to undertake, 

 and to some extent insuperable in its difficulties, since these lists 

 should be read through as a whole, and so to some extent re-written. 



1 See Scientijic Froceedings R. D. S., vol. v., pt. i., p. 17. 



