62 



The order of events, determining the relationship between 

 the tufaceous material and the lava eruptions, may be sug- 

 gested as follows : 



{a) A primordial lava flow, which originated near the pre- 

 sent small lake, on the western base of the mountain, 

 ana flowed over the old land surface before any ash 

 vas ejected, and, therefore, before the volcanic cone of 

 tufaceous material existed. 

 (h) The great north-west fissure, which had its origin after 

 a considerable thickness of ash had accumulated, and 

 the cone was approximately developed to its maximum 

 height, 

 (c) The great western lava field had its chief period of acti- 

 vity subsequent to the formation of the tufaceous crater, 

 and probably marks the closing stages of the volcanic 

 energy. It is possible that this fracture of the crust, 

 on the western side of the mountain, and the outflow 

 of molten material may have supplied the vent which 

 relieved the subterranean tension and permitted the 

 extinction of its fires. That the volcanic energy was 

 in a state of decadence is seen from the absence of any 

 one great stream of lava. The lava had little force 

 behind it, and did little more than scar the surfaces of 

 the fissures by which it found an exit. 



