OUTLETS OF THE ST. JOHN KIVEH. 47 



doubled over on itself. This over-folding has revealed 

 the existence of another profound fault in the earth's 

 crust within the city limits : it runs along the Marsh 

 and Valley, and the upper part of the harbor, from Mill 

 street past the Straight Shore to the Lunatic Asylum, 

 and beyond. (See map on page 56). 



On the south side of this great fault the earth's crust 

 has sunk down to the depth of three-cpiarters of a mile ; 

 or, vice-versa, the crust on the north side has risen to that 

 extent, and the covering of Cambrian rocks with its 

 entombed trilobites, molluscs and graptolites, or hydra- 

 like animals, has been completely swept away by the 

 vast denudation of subsequent ages. The weakness of 

 this fault lino helped to produce the valley which now 

 exists along the City Road, and the upper part of the 

 harbor which liere forms a part of the outlet of the St. 

 John. 



Denudation as well as faulting has helped to form these 



VALLEYS. 



Another part of the outlet is more clearly the result 

 of denudation or wear of the rocks. In the Laurentian 

 rocks which cross the liver at the " Falls," or rapids, 

 there are some bands softer than others. One of the soft 

 bands is that of shales, etc., which contains the graphite 

 beds ; this band is enclosed between limestones on the 

 south and quartzites on the north, and \femg softer than 

 the enclosing bands has given rise to the basin between 

 the Upper and Lower " Falls." The quartzites on the 

 north, form the ledges which obstruct the passage of the 

 water of the river at the " Upper Falls," and the lime- 

 stones on the south form cliifs on each side of the gorge 

 at the "Lower Falls." On the west side of the river rn> 

 rocky ledges show between these points, but the shore 

 consist of Boulder clay and other surface deposits. 



