and Physical Structure of the adjacent Country. 127 
same reck, and when the extensive waste of waters poured 
over the precipice at Queenstown, before they had worn out 
the channel (c) in the solid: rock. 
Before adver ting 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 
140 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 (7), 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 i 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 fhe 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 doin 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 fig. 23. and fig. 24.) would 
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 (f/f), aad 
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- 
