342 Canadian Record of Science 



less so if the contents were the Essexite which now form 

 its sides and floor. 



If, on the other hand, we assume that the solid masses 

 of Trap which now stand on each side of the Valley 

 were formed by the intrusion of liquid matter from 

 some great subterranean reservoir, into two cavities 

 which -existed where they now stand, with a considerable 

 wall or mass of limestone between them, as shown by the 

 sketch Fig. 1, which may have been fractured in many 

 places but was of sufficient strength to contain it until 

 the lava had become hardened, we have the conditions 

 under which the elevations on the two sides of the valley 

 could have formed. 



We may also assume, from the well-known general 

 conditions present in Volcanos, that the energy which 

 projected the lava into these cavities may have for the 

 time, spent itself, and that the Mountain remained in 

 a quiescent condition a sufficient time, possibly for long 

 ages, as in the case of Vesuvius before the eruption of 

 A.D. 79, and so allowed the melted matter to become 

 cooled. 



If then, as is also frequently the case, there was a 

 renewal of activity at a later period, there would be 

 nothing improbable in supposing that the already frac- 

 tured and weakened limestone between the two rigid 

 masses of Trap was blown out of its bed, not probably 

 at once, but by a series of long continued explosions, 

 until there was formed an immense crater, a mile in 

 length and half a mile in width. The fact that the 

 ground at Cartierville is strewn with huge blocks of 

 limestone and Essexite may have some bearing on this 

 point, although it is possible they may have been carried 

 there by ice. v 



It is to be noted here that at the Westmount end of 

 the crater the conditions are somewhat different from 

 those which prevail in the walls surrounding the other 

 part of it, which are of solid Essexite. At this point 

 the Avail, especially at the northeastern end, is princi- 



