and Physical Structure of the adjacent Country. 127 



same rock, and when the extensive waste of waters poured 

 over the precipice at Queenstown, before they had worn out 

 the channel (c) in the sohd rock. 



Before adverting to the causes which have combined to 

 effect the excavation of the chasm (c), 7 miles in length and 

 200 feet in depth, it may be proper to say something of the 

 strata which form the table land, and in which the excavation 

 is made. The diluvial sand varies in thickness from 10 to 

 1 40 feet ; under this is a bed of hard limestone, containing a 

 few imperfect organic remains : this stratum is about 90 feet in 

 thickness, it extends nearly in a horizontal direction over the 

 country, and forms the bed of the river above the Falls. This 

 limestone rests on a bed of loose shale rock (^), nearly of the 

 same thickness : it is exceedingly fragile, and crumbles into 

 small pieces on being removed from its native bed ; the shale, 

 also, contains some pieces of dark argillaceous limestone. 

 Had all the strata been solid limestone, there is great reason 

 to believe that the erosive action of the water would have been 

 very slow, and many generations might have passed away 

 without any sensible change taking place ; but the vast mass 

 of waters, breaking, with inconceivable force, on the softer 

 shale which forms the base of the hard rock, the foundation is 

 thus undermined, and the harder rock breaks down, in consi- 

 derable masses, for want of support. 



It is highly probable that the Lakes Superior, Michigan, 

 Huron, and Erie were once united, and formed one vast in- 

 land sea, which poured its waters down the Missouri and Mis- 

 sissippi into the ocean ; even at present, some of the branches 

 of the former river (in high floods) interlock with the rivers 

 that run into Lake Superior. The abrupt termination of the 

 table land at Queenstown (see ^^. 23. and Jig, 24.) woul^i 

 indicate a subsidence of the country round what is now Lake 

 Ontario : such a subsidence, if admitted, would very naturally 

 explain the circumstances at present existing. The waters of 

 the great lakes to the west would, at first, rush over the whole 

 precipice at Queenstown, and take a northern direction by the 

 river St. Lawrence. As the waters gradually became lower, 

 they would be confined between the diluvial banks {,//), and 

 finally begin to furrow the passage or chasm in the solid rock 

 which we at present observe. The immense force of the 

 water, as before stated, acting on the loose shale, it would be 

 carried away in the state of mud, and the overhanging lime- 

 stone, being left without support, would fall down in large 

 masses, which would be broken by the fall, and would be worn 

 and carried away by the violence of the current. This pro- 



