io A NATURALIST IN THE GREAT LAKES REGION 



and makes some short canyons near Joliet, one of which is included 

 in Delwood Park. Sugar Creek has cut a gorge nearly fifteen 

 feet deep in the suburbs of Joliet, crossed by the Chicago & 

 Alton main-line tracks going south. 



Water may be quite as efficient an agent of land destruction 

 when running underground as it is when on the surface, particu- 

 larly in limestone regions. Percolating through soil filled more 



FIG. ii. Clay pinnacles, erosion remnants, near Lakeside, Mich. Note 

 white pine, Pinus strobus, and juniper, Juniperus communis, on crest. Inset, 

 details of other nearby pinnacles. 



or less with disintegrating organic matter that liberates CO 2 the 

 water becomes charged with this gas. In such a condition its 

 power to dissolve limestone is relatively great. Following some 

 crevice, joint, or bedding-plane, the water excavates the rock, 

 carries it away in solution, and underground caverns are formed, 

 at times of great extent and wonderful beauty. While none are to 

 be found in the immediate Chicago region except small ones 

 discovered as the limestone is quarried, yet we are near enough 



