Was Mount Royal an Active Volcano ? 323 



the general surface of the country is now much lower than 

 it was at some former period, and its relation to the height 

 of the mountain very different from what it is at present. 



Since the earth became cooled and hardened, there has 

 been a constant succession of changes in the position and 

 location of the materials which formed its surface. 



These have been disintegrated by the effect of the 

 atmosphere, rain, frost, and other influences, and redistrib- 

 uted by the action of water, forming in this way beds and 

 banks which eventually hardened into rocks, which enclose 

 and preserve the various forms of life existing at the 

 time they were deposited, the total mean thickness of the 

 accessible part of these fossiliferous rocks in Europe being 

 estimated by Geikie at 75,000 feet or about 14 miles, 

 while single beds of limestone over 1,000 feet in thickness 

 are described by Logan as occurring in the Laurentians, 

 and the total thickness of the latter formation has been 

 placed at 30,000 feet, or over 5^ miles. 



Bearing in mind the tremendous scale on which these 

 operations of nature have been carried on, the fact will be 

 easily realized that there might have been a thickness of 

 several hundred feet of strata above that of the present 

 level, and that it might even have stood much higher than 

 the summit of the mountain as it appears to-day. 



The facts which have so far been ascertained would 

 seem to justify the opinion that this was the case. Logan 

 estimates the thickness of the Trenton with the Black 

 Eiver and Birdseye formations at Montreal at 650 or 700 

 feet, and the Chazy at 150 feet, while the total thickness 

 of the Hudson Eiver formation, the highest member of the 

 Lower Silurian, is placed at 2,000 feet, of which the Utica 

 formation would amount to about 300 feet, although in 

 places the thickness of the latter was much greater, a 

 boring at Laprairie showing a depth of over 1,000 feet. 



It is needless to say that no absolutely certain measure- 

 ments of the hiohest level of the Silurian strata can be 



