and Siibterranean Water Storage. 73 



action is going on, where water is heated or converted into 

 steam, and whence jets of mineralized water may be forced 

 upwards. Such conditions modify and complicate the phe- 

 nomena, but they do not affect the general explanation. The 

 disturbances that have resulted only in the tilting or partial 

 lifting up of strata act in one way, and those disturbances that 

 have broken and displaced them act in another, so far as water 

 is concerned, but both help in the distribution and circulation 

 of the water through the earth. So, again, the filling up of 

 fissures caused by disturbances may entirely shut off whole 

 districts from the passage of water, and cause the water to collect 

 in certain strata to an unusual extent. This is a fact very 

 familiar to all who have had to do with coal mining, where 

 faults (as these disruptions of strata are called) are very common 

 and systematic, and where very serious accidents have happened 

 from breaking through them when they shut ofl' water from sur- 

 rounding strata. On the other hand, they as frequently carry off 

 as hold back water ; and in the broken coal-fields of England 

 and Belgium they always play a very important part in the 

 underground drainage. 



Those fractures of rock, that are technically called axes (anti- 

 clinal or synclinal), also affect the underground passage of water. 

 Their action may best be studied in the natural sections pre- 

 sented in cliffs or railway cuttings. Such sections show the 

 strata dipping away from or towards each other, and meeting at 

 an angle. It is evident that if of such strata some are permeable 

 and others impermeable, the water passing through the former 

 will have a tendency to escape at the angle made by the rocks 

 that have been thus broken while being lifted up. Practically, 

 then, the effect of faults and axes will be to cany the water down 

 to the permanent level of absolute saturation, and assist in this 

 way in its general progress through the interior of the earth. 



Water thus passing into rocks from above, and passing also 

 amongst them, cannot but be regarded as " circulating " in the 

 earth's interior. Of such circulation evidence is offered by 

 every natural and artificial spring, whether issuing from a 

 hill side or rising from an artesian boring in a valley, and 

 by the condition of rocks seen in quari'ies or reached in mines. 

 It is owing to the presence of water in and amongst rocks, and 

 in the fissures that are formed in them during and after elevation, 

 that their various metamorphoses or changes of appearance can 

 be produced. Pressure, together with the chemical action 

 arising from heat, no doubt affects strata ; but the changes that 

 have taken place involve not only the mechanical presence, but 

 the chemical action of water, dissolving away many substances as 

 it passes through a rock, and leaving behind many others. Even 



