160 



GEOLOGY OF LA SALLE COUNTY. 



Covmty," Keet & Co., Chicag-o, 1877, tint the flow of 

 artesian wells, at least of those about Ottawa, is ir re ov- 

 ular, that is, they deliver a g-reat^r quiiitity of water 

 per hour at one time than at another. Few experi- 

 ments have been made in this direction, and one hears 

 much loose talk on the subject, but Judge Caton's 

 experiments were carefully made and are convincinof, 

 he was unable to discover anything- like regfularity in 

 the variation or to connect it with any cause. 



Our friend Mr. T. D. Catlin informs us thai he 

 has a well 1,800 feet deep, which was, when first bored, 

 capable of raising- water some 160 feet above the 

 Courthouse Square. This well is tubed 1,730 feet 

 from the top, the remaining- sevent}^ feet being- through 

 shales which it was deemed unnecessary to tube. For 

 a time the well worked perfecth^; then it showed signs 

 of weakness, and finally raised no water to the top of 

 the bluff, and it was supposed that it had g-iven out. 

 But after a time it showed sig-ns of recovery, and now 

 flows, but less strong-ly than at first. He accounts for 

 its failure in this way: A column of water 1,900 feet 

 long- has a pressure equal to about 58 atmospheres, or 

 870 pounds per square inch, more than four times the 

 pressure carried by the strong-est locomotive boilers. 

 This immense force exerted on the shale forced the 

 water through it into some adjacent cavities and took 

 the water from its course through the well in some 

 other direction. At length, this reservoir being filled, 

 the water returns to its former course. 



Another reason may be given for a part of the 

 change. The water of artesian wells, as well as of all 

 others, depends originally on the quantity of rain fall- 

 ing- somewhere, which, soaking into the earth and 

 being confined between impervious strata, is obliged to 

 pursue a certain course, and whenever an opening is 



