and the Storage of Water. 
11 
the ffeoloffical character of the district, the state of cultivation 
of the soil, and the season of the year. 
The geological structure and the physical outline of a dis- 
trict affect very greatly the quantities of rainfall discharged 
off the surface or absorbed by the land. If the district be of 
an impermeable character with steep slopes, a large portion of 
the rainfall will run off into the water-courses. If, on the other 
hand, the soil be porous and the contour of the district flat, the 
greater portion of the rainfall will be absorbed. The dip of 
the strata also has an important bearing on the amount absorbed 
or discharged off the surface. A permeable stratum may be so 
thrown up as to dip in a direction opposed to the slope of the 
drainage area, and carry the rain falling on its surface away 
from the natural streams of the watershed to supply springs in 
another district. 
Fig. 1. — Geological Section of uncomformahlc strata, sJiowing Permeable 
Beds dipping aicay from the Drainage Area of their outcrop. 
In the accompanying diagram the limits of the watershed are 
shown by the letters A C. Rain falling on the surface between 
A and B would run down and pass away by the water-course 
along the valley at H. That, however, falling between B and C 
would, to a very great extent, be absorbed by the permeable 
stratum which crops out at the surface, and, sinking down till it 
met the impermeable stratum, run off in the direction B S, and 
find escape at the spring s, contributing to -the supply of the 
water-course of the adjoining watershed. Again, rain falling on 
the permeable stratum between A and K, would be absorbed and 
sink down in the direction K F, and be held there as in a reservoir 
by the impermeable stratum below. When the space between 
F and D became supersaturated or full, the water would flow over 
D and pass down towards S, and there find its escape. The 
supply from this source would be intermittent, the quantity 
varying probably as the rainfall. A well sunk through the 
