270 Ground Water, Wells, and Farm Drainage 



feet of water to be discharged under the conditions for the 

 sand. 



335. General Movement of Ground Water Across Wide 

 Areas. The waters which supply artesian wells and many 

 springs, where the discharges take place through openings 

 in overlying impervious beds, are often obliged to travel 

 long distances, even 100 or more miles, before reaching 

 their outlets. But this cannot occur with such low rates of 

 flow as those observed in (334) and it is clear that nearly 

 the whole movement across long distances must take place 

 through rock fissures and along bedding planes, the water 

 seeping out of the rock into these as it does into river chan- 

 nels and lines of tile drains. 



336. Fluctuations in the Rate of Flow of Ground Water 



When arrangements are made to automatically record the 

 rate of discharge of water from springs, artesian wells or 

 lines of tile drains it is seen that the flow is not uniform, 

 varying not only with the season, but often daily and even 

 hourly. 



Fio. 100. Showing observed barometric changes In the rate of flow of 

 water from a spring, and the apparatus for recording it. Lower curve, 

 record of spring. 



In Fig. 100 is shown an autographic record of the dis- 

 charge of water from a spring during 13 days, together with 

 the changes in barometric pressure as recorded by a baro- 

 graph 45 miles to the west of the spring. The method of 



