O'Reilly — 0« the Dates of Volcanic Eruptions. 393 



examples can hardly yet be looked upon as more than coincidences. 

 At many Tolcanic vents the eruptive energy manifests itself with 

 more or less regularity." 



The author then cites the cases of Stromboli, Etna, and Vesuvius: — 

 "Much more striking, however, is the case of Kilauea in Hawaii, 

 which seems to show a regular system of grand eruptive periods. 

 Dana has pointed out that outbursts of lava have taken place from 

 that volcano at intervals of from eight to nine years, this being the 

 time required to fill the crater uj) to the point of outbreak, or to a 

 depth of 400 to 500 feet. But the great eruption of 1868 did not 

 occur until after an interval of eighteen years." (Dana's remarks 

 prove that two successive eruptions took place at sun-spot periods, 

 one in + 1848-6, and the other in -1867-2, the interval being 18-6 

 years.) "The same author suggests that the missing eruption may 

 have been submarine."^ 



As regards his references to the pp. 250 and 259 of his text-book, the 

 following lines bear generally on the question : — "Many difficulties, 

 however, remain yet to be explained before our knowledge of volcanic 

 action can be regarded as more than rudimentary," p. 250. 



In section ii., part 1, " Earthquakes," p. 259, he says, *'Erom 

 what was stated at the beginning of the present section, it is evident 

 that some connexion may be expected to be traceable between the 

 frequency of earthquakes, th^ earth's position with regard to the moon 

 and sun on the one hand, and changes of atmospheric conditions on 

 the other." He then cites the observations and conclusions of Schmidt 

 and Perry, and adds: — "No connexion has yet been satisfactorily 

 established between the occurrence of earthquakes and sun-spots." 

 He says, p. 248, " There is indeed strong evidence that among the 

 consequences arising from the secular contraction of the globe, masses 

 of sedimentary strata, many thousands of feet in thickness, have been 

 crumpled and crashed, and that the crumpling has often been accom- 

 panied by such an amount of heat and evolution of chemical activity 

 as to produce an interchange and rearrangement of the elements of 

 the rocks, this change sometimes advancing to the point of actual 

 fusion , . . Along lines of elevation the pressure is relieved and con- 

 sequent melting may take place. On these lines of weakness and 

 fracture therefore the conditions for volcanic excitement may be con- 

 ceived to be developed — water, able soonest to reach there, the 

 intensely heated materials underneath the crust may give rise to 



1 " On the Periodicity of Eruptions," see Kluge, "Neues Jahrbuch," 1862, 

 p. 582. 



E.I. A. PEOC, SEE. III., VOL. V. 2 P 



