274 Ground Water, Wells and Farm Drainage. 



coincident in phase with those which occurred in the dis- 

 charge of water from a spring. Changes much more vio- 

 lent than these and of shorter duration are shown in Fig. 

 106. Fluctuations like these occur at times of violent 

 thunder storms and are due to changes in air pressure and 

 not to rainfall. In this case the changes occurred in a 

 drilled well 60 feet deep with 6 inch steel casing to rock 

 and the changes in the level of the water were so great that 

 the instrument had to be set over three times to keep the 

 pen on the record sheet 



