272 Ground Water, Wells and Farm Drainage. 



much as if a rain had occurred and percolation had in- 

 creased the hight of the ground water itself. Fig. 102 

 shows the changes which did occur in the level of the water 

 in surface wells near the system of tile drains in question. 

 The curves were produced at the same time by self-record- 

 ing instruments. Fig. 103 shows another series of diurnal 

 fluctuations where the changes in level were measured 

 twice daily, in the morning and at night, and Fig. 104 

 shows the conditions under which these changes occurred. 

 The lower curve represents the "changes in the inner well 

 while the upper curve shows those in the outer well where 

 the water percolated from ahove the stratum of clay under 

 the influence of the air pressure caused by the diurnal 

 changes in temperature. 



FIG. 108. Snowing diurnal changes in the Fio. 104. Showing th toil con- 

 Level of the ground water measured twice ditions under which the changes 



daily in surface wells. 



of Fig. 103 took place. 



339. Fluctuations in the Level of Water in Wells. In all 



ordinary wells, whether they are deep or shallow, the water 

 is seldom at rest, the surface continually either rising or 

 falling through varying distances, and Fig. 105 is a record 

 of one such series of changes which it will be seen are nearly 



