20 THE CAXIFORNIAN EARTHQUAKE OE 1906. [Feb. 1909, 



was one of extreme difficult}' ; but the paper, if it did net afford a 

 solution, had at least the merit of raising the question. 



The Author, in reply, said that he was unable to form any con- 

 clusion as to the manner in which the stresses were produced, or 

 as to their exact nature. As regarded the connexion of faults with 

 earthquakes, it was undeniable that they often determined a local 

 increase of violence of shock, and to this extent could be regarded 

 as the cause of earthquakes ; but the conclusion to which he had been 

 driven was, that although the presence of pre-existent fractures 

 might determine the localization and distribution of the violence of 

 the shock, the disturbance was really independent of them, and that 

 the position of earthquake-origins and the forces to which they 

 were due were independent of the leading structural features of 

 the district and of the forces and movements by which these were 

 produced. 



