Hilgkndorf. — Artesian Wells in the Christchurch Area. 



145 



The Weekly Fluctuation. 



The following graph of the weekly averages of the readings of the 

 well shows clearly the relation between the static level of the well and 

 the rainfall. 



Fig. 2. — Weekly Averages of Height of Well, and Weekly Totals of Rainfall 



at Lincoln. 



It is clear from this graph that the well rises whenever rain falls, and 

 that the rise in the well is approximately proportional to the rainfall. 

 This result was anticipated from the work of Hutton* and Speight, f but 

 it was considered impossible that the rainfall at Lincoln could be respon- 

 sible for the rise in the well there, since, as before mentioned, the well 

 draws its water from 341 ft. below ground-level. 



Lincoln is situated on the Canterbury Plain, fourteen miles from the 

 sea. The plain is about fifty miles wide, and slopes upwards from the 

 sea to the mountains, at whose feet its level is about 1,300 ft. It is com- 

 posed of a coarse gravel interstratified (especially in its coastal portions 

 near Christchurch) with clay, peat, &c, as described by Speight (loc. cit.). 

 On the supposition that the lower strata have been laid down at a steeper 

 angle than those now on the surface, the water-bearing stratum tapped by 

 the Lincoln College well should outcrop on the surface of the plain some 

 miles above Lincoln, and it would probably be the rain falling on this 

 outcrop that would supply the well. This idea is embodied in the following 

 diagrammatic sketch, where the heavy lines show the clay strata between 



Trans. N.Z. Inst., vol. 28, p. (554. 



t Trans. N.Z. Inst., vol. 43, p. 420. 



