PECULIARITIES OF BEHAVIOR OF WELLS 135 



and in warm climates, where freezing never occurs, may be 

 overlooked. Its presence is, however, abundantly demon- 

 strated. Even if no indraft is observed, it is noted that the 

 blowing is weak or ceases at times, so that there is a rhythm in the 

 movement of the air. In humid regions the blowing is, as a rule, 

 most marked before rain storms, and the sucking or indraft of air 

 occurs in clearing weather after a storm. In other words, the 

 blowing occurs during periods of low barometer and the indraft 

 occurs in periods of high barometer. The blowing may be asso- 

 ciated with some particular direction of the wind, as would be ex- 

 pected from the fact that the direction of the wind in rain storms 

 is different from that prevailing in clear weather. Some wells 

 show fluctuations with very small changes of barometric pressure, 

 even with the diurnal changes, blowing at times of low pressure, 

 as at 3 A.M. and 4 P.M., and sucking at times of high pressure at 

 10 A.M. and 9 P.M. In some wells there is a noticeable " lag" in 

 the phenomena, the blowing and sucking continuing an hour or 

 more after the limits indicated. 



Sucking Wells. Wells that suck in air at times are common, 

 but those with continuous indrafts are very rare. Two such 

 "sucking" wells have, however, been reported in Tertiary lime- 

 stone near Boston, in southern Georgia. Where indraft alter- 

 nates with outdraft jhe movement has a direct relation to baro- 

 metric changes, but where the indraft is continuous no such 

 relation is observed, the phenomena apparently being independ- 

 ent of barometric pressure. In the wells noted above the air 

 is sucked in by streams of water running in caverns in the 

 rock. 



Freezing of Wells. -- Throughout many of the Northern states 

 much trouble is caused by the freezing of wells, not so much with 

 the shallow dug wells as with the deeper drilled ones. Many wells 

 in the North can be kept in use during the winter only with the 

 greatest difficulty, so that the determination of the cause of the 

 freezing and of means for its prevention is of great practical 

 importance. 



