138 PRINCIPLES OF STRATIGRAPHY 



V. Underground Water (Ground Water). 



Ground water is that part of the hydrosphere enclosed within 

 the pores of the rock of the earth's crust, and either circulating by 

 slow movements within the crust, or remaining stagnant within its 

 pores. 



Classification of Ground Waters. 



According to the mode of origin, ground water may be divided 

 into three types. 



A. Meteoric or Pluvial Waters, or those derived from rain or 

 snow and penetrating into the crust from above. These form the 

 vadose circulation. 



B. Connate JVaters, or those buried originally with the sedi- 

 ments in which they occur, and varying according to their derivation 

 from fresh to marine waters. This is the fossil water, and to be 

 conserved must remain stagnant within the pores of the rock. 



C. Maguiatic or Juvenile Waters, or those given off by cooling 

 magmas and in a sense generated anew by the combining of gases 

 from the igneous mass. 



Some observers, notably \'an Hise and his followers, would re- 

 gard all ground water as of meteoric origin, and consider the high 

 temperature and mineral content of such waters, originally cool and 

 nearly pure, as due to a descent into regions of high temperature 

 within the depths of the earth, or their coming in contact with 

 heated igneous masses, and the consequent impartation of heat and 

 thermal solvent power, so that both their temperature and mineral 

 content are acquired properties. Other workers in this field, notably 

 Eduard Suess and J. F. Kemp, have insisted on the magniatic ori- 

 gin of many if not most of the heated and mineral-laden waters, 

 the temperature and mineral content of which are, therefore, pri- 

 mary or a part of their original character. It is this class of waters 

 which is believed to be responsible for most of the ore deposits 

 within the older rocks, and to such an origin may perhaps also be 

 traced most of the hot and mineral springs of the present day. Re- 

 cent experiments at Kilauea have resulted in the actual condensation 

 of water from gases given off by the lavas. 



The term connate waters was proposed by Lane {24:503), who 

 calls attention to a class of waters which has been much neglected. 

 Walther, more than any other writer, has insisted on the signifi- 

 cance of fossil sea waters as an important source of salts concen- 

 trated from them by surface agencies under arid climatic conditions. 



