DISTBIBUTION OF EARTHQUAKES IN TLVIE. 237 



In making this statement we must not overlook the 

 fact that in geological time, as testified by the records of 

 our rocks, volcanic action, and with it probably seismic 

 action, has been continually shifting, first appearing in 

 one area and then in another, and even in the same area 

 we have evidence to show that these have periods of 

 activity and repose successively succeeding each other. 

 Thus in Britain, during the Palaeozoic times, we have 

 many evidences of an intense volcanic activity. During 

 the Mesozoic or Secondary period volcanic energy appears 

 to have subsided, to wake up with renewed vigour in the 

 Cainozoic or Tertiary period. 



During this latter period it is not at all improbable 

 that Scotland was in past times as remarkable for its 

 earthquakes as Japan is at the present day. 



Later on it will also be shown that earthquakes are 

 concomitant phenomena, with those elevatory processes 

 which we have reason to believe are slowly going on in 

 certain portions of the earth's crust. If, therefore, we 

 are able by the examination of the rocks which constitute 

 the accessible portions of our globe to determine which 

 periods were characterised by elevation, we may assume 

 that such periods were also periods of seismic activity. 



Amongst these periods we have those in which various 

 mountain ranges appeared. Thus the Grampians, and 

 the mountains of Scandinavia, were probably produced 

 before the deposition of the Old Eed sandstone. The 

 Urals were upheaved prior to Permian times. The chief 

 upheaval in the Alps took place after Eocene times. The 

 Kigi and other sub- Alpine mountains were formed after 

 the deposition of the Miocene beds. About this same 

 time the Himalayas were upheaved.^ 



The earthquakes which from time to time shake those 

 ' Karnsay, * Geological History of Mountain Ch&ins,* Mining lojirna. 



