52 



GEOLOGY OF IvA SALLE COUNTY. 



Chalybeate or iron springs are found in man}^ 

 places issuing- from the coal measures. Some of these 

 are heavily charged with sulphate of iron, and are 

 clear as crj^stal, and of a temperature of 50 ^ degrees 

 or less. We have found them about Streator, along- 

 the Big Vermillion, and east of Utica, along the north 

 bluff. ^ 



A remarkable nest of springs exists about two 

 miles southwest of Ottawa, on the south side of the 

 Illinois, flowing out of a vast mass of -tufa, or as it is 

 generally called petrified moss, true in that moss had 

 probably had something to do with its formation, but 

 wide of the mark in that there is nothing petrified. In 

 fact, petrifactions are rather scarce. We have casts 

 and incrustations, but seldom the thing itself, changed 

 to stone. These springs furnish a large volume of 

 clear, cool water, and do not now seem to carry 

 anv considerable quantity of lime in solution. It is 

 from these that the water is obtained to supply the 

 water trough by the roadside. 



Water holding much lime in solution, coming to 

 the air usually parts with most of the lime. This is 

 especially the case w^hen it flows over a moss covered 

 surface or in quantities sufficient to keep a surface 

 moist, or drops from a greater or less heighth. In all 

 these cases much of the water evaporates, leaving the 

 lime behind either incrusting mosses, grasses, twigs, 

 eto., or forming thin layers one upon another. When 

 it falls in drops we have a growth resembling an 

 icicle, and formed in the same way, while from be- 

 low if any of the w^ater drops off a little, column 

 grows upward. The icicle like growths, are called 

 stalactites, the upward growths from the bottom 

 stalagmites. They are generally found in caves, but 

 sometimes in crevices of the rock. Some such g-rowths 



