GEOIvOGY OF IvA SALLE COUNTY. 



67 



No. 13 is shorter than 12, is formed by two ravines 

 uniting-, but is much less imposing than 12. 



No. 14 comes into the valley at the east side of 

 Starved Rock. 



No. 15 enters the valley a little west of Starved 

 Rock, and is a very romantic and interesting- canon, 

 having' the lower part of its course at a low level, then 

 being- crossed b}^ a precipice, and the upper part, 

 yet deep, below the surface, at a hig-her level. 



No. 16 is shorter, about a half mile west of 

 Starved Rock, wild and picturesque. 



No. 17 is a larg-e and handsome g-org-e, reaching- 

 the Utica-Lowell road at the foot of the bluff. 



No. 18 is about a half mile west of the n.ad, and is 

 wonderfull}' beautiful in summer and must be ver}^ g-rand 

 when there is water flowing- over the precipices by 

 which it is crossed. 



On the Big- Vermillion there is but one canon. 

 Deer Park g-len. It is from seventy to ninety feet 

 from bottom to top of the encircling- rocks, about 

 ninety rods long, where it is terminated by an overhang- 

 ing wall forty feet high, beyond which extends a rocky 

 chasm more than 100 rods in length. 



These ravines represent the w^ork done by the 

 streams flowing through them, not always on the sur- 

 face but in the body of the rock, for it must be appar- 

 ent to the least observant that a considerable volume of 

 water flows through the rock and comes out in springs 

 at various levels. This water is not a neutral ag-ent, 

 but is constantly effecting changes of importance, bear- 

 ing particles of the rock, dissolving out of the mass the 

 lime and iron which form the cement binding |^it to- 

 gether, and thus rendering it softer and less coherent. 

 Thus these streams, when the country was a wilder- 

 ness, less irregular in their flow than now, cut out these 



