CLASSIFICATION OF SPRINGS 527 



Springs may be divided according to temperature into thermal 

 and non-thermal springs. Most non-thermal springs have tem- 

 peratures that are approximately the same as the mean annual 

 temperature of the air of the region in which they are found. The 

 division between thermal and non-thermal waters is usually fixed 

 at 70° F., but 20° to 25° above the mean for the region might be 

 preferable. Thermal springs are usually called "hot," but those 

 of slightly lower temperature are sometimes called "warm." Cold 

 springs have temperatures below normal. The water of some cold 

 springs is derived from the melting of ice or snow; that of others, 

 being quickly transferred from a higher to a lower elevation through 

 open channels, retains the temperature of its point of origin on 

 emergence. 



Boiling springs have a sandy bottom, through which the water 

 emerges with some force. The sand is constantly agitated and 

 appears to boil. Bubbling springs, also called boiling springs, are 

 due to the emission of gas or vapor with the water. Certain hot 

 springs actually boil in the ordinary sense. Usually emission of 

 air or gases gives the impression of ebullition. Carbonated springs, 

 which emit carbon dioxide, are the most common bubbling springs. 

 Nitrogen, hydrogen sulphide, sulphur dioxide, marsh gas, and other 

 gases have been found in spring waters. Bubbling is produced 

 also by the emergence of water from a well-defined opening under 

 considerable pressure into a pool of water. The surface of the 

 water is domed, and slight fluctuations in volume or pressure give 

 a bubbling effect. 



Perennial or permanent springs flow throughout the year. 

 Intermittent or temporary springs flow only during or after rain. 

 Where evaporation is high the flow of springs is much decreased or 

 may cease during the warm season. Some springs flow only at 

 night because of a very delicate adjustment between supply of 

 water and evaporation. Periodic springs flow at full strength for 

 long or short periods, which are not closely related to the fluctua- 

 tions in rainfall. The periodic action is dependent on the exist- 

 ence of open cavities. Springs here classed as solution tubular or 

 cavern springs are most likely to have this characteristic. A 

 cavity is drained by a small but insufficient outlet. As water 



