USES OF WATER 115 



hundred to one, according to Pascal's Law a pressure of 

 one pound on the smaller piston will transmit a force of 

 one hundred pounds to the larger piston. By increasing 

 the ratio of the larger piston to the smaller piston, we 

 can obtain enormous pressures. Hydraulic presses are 

 used in many places where a great force is needed ; as in 

 lifting jacks, cotton presses, iron testing machines, and 

 many others. 



It will be observed that while the hydraulic press exerts 

 a very great force it acts quite slowly through a given 

 space. For example, if the ratio of the areas of the pistons 

 is 100 to 1 and the smaller piston mpves one inch, the 

 larger piston will move but TSTF of an inch, so that the 

 products of the force times the distance which the re- 

 spective pistons move are always equal. 



Artesian Wells are dependent on the principle of trans- 

 mission of pressure by liquids. Water percolates through 



FIG. 105. Artesian Basin, Showing Arrangement of Rock Strata. 



the soil and finally becomes entrapped under an imper- 

 vious stratum of rock through which it finds no outlet. 

 If a well is bored through this stratum, water gushes up 

 often to a considerable height. Figure 105 shows a dia- 

 gram of what the geologists call an artesian basin. Water 

 enters the stratum A at the outcropping ends. The im- 

 pervious strata hold it entrapped until a boring is made. 

 Probably the most famous well is at Grenelle near Paris. 

 It is 1740 feet deep and delivers over 500 gallons of water 

 a minute at a temperature of 84 Fahrenheit. The 



