PKEDICTION OF EAKTHQUAKES. 805 



activity beneath the earth crust, or whether they are only 

 due to vibrations of the earth crust produced by variations 

 in atmospheric pressure, has yet to be investigated. 



Other phenomena which may probably forewarn us of 

 the coming of an earthquake are phenomena resultant on 

 the stresses brought to bear upon the rocky crust previous 

 to its fracture, or phenomena due to changes in the posi- 

 tion and condition of heated materials beneath the earth's 

 surface. Amongst these may be mentioned electrical 

 disturbances, which appear to be so closely related to 

 seismic phenomena. 



At the time of earthquakes telegraph lines have been 

 disturbed, but as to what may happen before an earth- 

 quake we have as yet but little information. The subject 

 of earthquake warning is of importance to many countries, 

 and is deserving of attention. 



As our knowledge of earth movements, and their at- 

 tendant phenomena, increases, there is but little doubt 

 that laws will gradually be formulated, and in the future, 

 as telluric disturbances increase, a large black ball gradu- 

 ally ascending a staff may warn the inhabitants on the 

 land of a coming earthquake, with as much certainty as 

 the ball upon a pole at many seaports warns the mariner 

 of coming storms. 



