THE INTERIOR OF THE EARTH. 



457 



He therefore maintained, with Davy, the hypothesis of a non-oxidized 

 nucleus which becomes an inexhaustible chemical source of heat by 

 contact with the already oxidized crust. In this view of the matter, a 

 volcano is simply a permanent fissure and channel of intercourse be- 

 tween the non-oxygenated nucleus and the liquids lying upon the 

 oxygenated bed. Whenever this passage of the liquids to the nucleus 

 takes place, elevations of the earth occur from the increase of volume 

 due to oxidation. The heat generated by these chemical actions is 

 propagated at once toward the exterior and interior of the globe, and, 

 in proportion as the oxidation of the crust progresses, the seat of these 

 chemical actions is carried deeper. This, a difficult theory to sustain, 

 has no longer any adherents. 



To the objection of the power of the tides it may be further said 

 that, examined more carefully, they would probably be found to pro- 

 duce an entirely inappreciable flexion of the solid crust far from suf- 

 ficient to cause any disruption. Indeed, it is a question to be consid- 

 ered whether earthquake phenomena do not indicate the existence of 

 subterranean tides. This is a matter that has formed the object of 

 over thirty years' researches by M. Alexis Perrey, Professor of the 

 Faculty of Sciences at Dijon. Professor Perrey has compiled all the 

 observations of earthquakes from the middle of the last century to the 

 present time, and, in grouping the various facts collected during these 

 one hundred and twenty-five years, he has been able to adduce evidence 

 of a connection between the frequency of earthquakes and the phases of 

 the moon. If the phenomena are compared with the lunar month, two 

 maxima will be seen at the periods of the syzigia (new and full moon), 

 and two minima during the first and last quarter. In the following 

 table the results of observations for three periods are given, the earth- 

 quake-days being grouped in the weeks corresponding to the moon's 

 four phases, the new and full moon groups and the quadrature groups 

 being separated : 



It would thus appear that the shocks occur more frequently at 

 those periods when the sun and moon can combine their action on the 

 liquid particles of the interior of the globe. 



M. Perrey has also compared the earthquake-periods Avith the times 

 of perigee and apogee, that is, the moon's nearest point in her orbit to 



