296 On the Boulders of Primitive Rocks found in Ohio, $>c* 



What is called the falls is a natural dyke of limestone twenty 

 two feet high, crossing the bed of the river, and the water is 

 backed up by it, as it would be, in anyplace, by a mill dam of 

 the same height — If the dyke were removed, the fall would 

 disappear. 



The justly celebrated traveller Volney (who examined the 

 north western territory) was of opinion, that " it is an eleva- 

 ted plain, about as high as the Allegany range." Actual 

 measurements prove that he was mistaken, as to the height 

 of this plain, although they prove also, that it is in truth an 

 " elevated plain" and render it highly probable, that the 

 streams, flowing down its north side, would find descending 

 ground to Hudson's bay, were it not for the intervention of 

 the great valley of the St. Lawrence, as the waters from the 

 north side of the continuation of this plain, west of the Mis- 

 sissippi, find their way into the northern ocean. To suppose 

 therefore, this elevated table land to have been the bottom 

 of an immense lake, or to suppose, that a current of water 

 has swept some northern mountain up, on to this plain and 

 scattered its fragments over it, are suppositions which appear 

 altogether inadmissible. 



How then came these boulders in their present situation ? 

 In the present state of knowledge, this question cannot be 

 answered. In the mean time, ignorance is preferable to er- 

 ror, and what is unknown may be examined. It may there- 

 fore be asked, why may not these rocks have been created 

 where they are now found ? If we have not seen the opera- 

 tions of nature in forming primitive rocks, it may be because 

 the process is so slow as to elude observation. It is evident 

 that some classes of rocks are constantly undergoing the 

 processes of aggregation and disintegration ; the primitive 

 as well as the secondary, are seen to decay and fall to pieces; 

 the quartz, the hardest mineral which enters into the com- 

 position of granite, is of constant growth, in all its crystal- 

 line and some of its amorphous forms, and from the uniform 

 analogies of nature, its aggregation into granite may be sup- 

 posed as probable as its aggregation into sandstones is 

 known to be certain. Again, why may they not have been 

 thrown out by earthquakes or volcanos ? The horizontal strat- 

 ification of the great vallies of the Mississippi is not entirely 

 uniform. In some places, the strata of limestone, in others 

 of sandstone and in more, of the slates have evidently been 

 disrupted and thrown out of an horizontal position, by some 



