12 Mr, Fairholme on the Falls of Niagara 



milar index to the length of time which has elapsed since the 

 first commencement of the present state of things on the sur- 

 face, and consequently having so direct and simple a bearing 

 on the geological character of the district in which it is found. 



It is perhaps not so well known as it ought to be, that al- 

 most the whole continent of North America consists of vast 

 plains, composed of secondary strata of various kinds; and 

 that calcareous formations in a horizontal stratification form 

 the leading characteristics in the geology of that country. 

 The prodigious lakes of Canada and the United States are 

 formed by the easy and gentle undulations of these secondary 

 strata; and the sea-like extent of these freshwater basins, 

 together with their generally low and swampy shores, exactly 

 correspond with the boundless extent of plain which sur- 

 rounds them on every side. The very circumstance of the 

 rivers of North America being navigable for so great a propor- 

 tion of their length, is sufficient to show the nature of the great 

 steppes through which they take their easy course towards 

 the ocean ; and the rapids, which form so interesting and 

 picturesque a feature in the inland navigation of the New 

 World, are obviously occasioned by those breaks and inter- 

 ruptions in the superficial strata for which calcareous forma- 

 tions are so remarkable. 



It is to one of these interruptions in the general level of 

 that part of the world that the cataract of Niagara owes its 

 origin. Two vast plains, or steppes (as they are termed in the 

 North of Europe), extend themselves in different directions. 

 One is spread over Upper Canada and New York towards the 

 north, while the other embraces the shores of Lake Erie and 

 its surrounding States towards the south-west. Between these 

 great plains there is a considerable difference of level ; and as 

 the former is lower than the latter, all the waters which are 

 drained from the one must experience a fall, more or less vio- 

 lent according to the nature of the line of demarcation over 

 which they must pass, before they can subside into the ge- 

 neral level of the other. 



In this particular case it happens that this line of distinc- 

 tion between these two plains is situated longitudinally be- 

 tween the two great lakes of Erie and Ontario, which are not 

 further removed from each other than about 36 miles ; and as 

 the difference of level is spread over an easy slope of 10 miles, 

 and does not amount to more than 330 feet, (or 1 foot of rise 

 in 160 feet of length,) the variation in the surface is so imper- 

 ceptible, unless in the neighbourhood of the rivers, that it is 

 not easily detected by a common observer in passing through 

 the country. 



This state of the case will be more clearly understood 



