DRAINAGE OF IRRIGATED SHALE LAND. 7 
a rather broad shale ridge is shown to come in from the northwest 
corner, becoming more sharply defined toward the south. In the 
southwest quarter is a portion of a draw or embayment in the shale 
formation, the slope of which is quite steep. Here the surface of the 
water follows very closely that of the shale. In the northwest corner 
the water conforms in a general way with the shale surface, but this 
iS a very wet seepage area and a point where the shale discharges 
considerable water into the soil above it. It is not to be expected that 
at such points the shale and water contours will agree closely. Far- 
ther down on the sharp-crested portion of the ridge there is a closer 
resemblance. 
Profile A of figure 5 (p. 29) is taken along the shale with highest 
grade and shows a marked agreement in slope between the water and 
shale. Profile B of figure 5 is taken across the better defined shale 
ridge and illustrates very clearly the conformity between the surfaces 
of the shale and water. Figure 7 (p. 33) shows the point of a well- 
defined shale ridge. The similarity between the shale and water con- 
tours should be noted. Profile C of figure 8 (p. 34), taken across this 
well-defined shale ridge, represents very much the same condition as 
does profile B of figure 5. Profile D of figure 8 is taken along a shale 
ridge and its point, and shows the water closely following the ridge 
up to the sudden dip or change in grade and then passing out into 
the soil, causing seepage conditions. 
ALKALI. 
Aside from the problem presented in the drainage of shale lands, 
complete reclamation for agricultural purposes is further compli- 
cated by the fact that lands of this type are often strongly alkaline, 
so that where they have become water-logged and have been allowed 
to lie idle for several seasons they have developed a decided alkali 
problem in addition to the one of drainage. 
As providing a criterion for determining the severity of the alkali 
problem of different tracts where drainage is a factor, it is believed 
that analyses of a limited number of samples of the soil water more 
nearly represent average conditions and consequently are of greater 
value than are analyses of the same number of samples of the soil. 
This view is held because the alkali in any tract of land always is 
more or less unequally distributed, and a wide range of results will 
be obtained from analyses of the soil, depending not only upon just 
what parts of the tract the samples are taken from, but also upon 
whether they represent the surface inch or surface foot or some other 
depth of soil. It is true, there will be also a variation in the quality 
of the soil-water from a tract, but in general the range is not so 
great as in the soil, and a few analyses will show whether it is high 
or low in salt content and will indicate the kinds of salts. Under 
