28 BULLETIN 502, U. S. DEPARTMENT OF AGRICULTURE. 
From a large number of borings the topography of the underlying 
shale was determined as indicated in figures 4 and 5. Shale was 
found near the surface on three-fourths of the tract, but no shale 
nor water could be found at a depth of 12 feet at the southwest 
corner, and the alfalfa there was in good condition. The strata of 
the shale underlying the tract are nearly vertical and badly broken. 
y VE 
Ground Surface------ 0 / 
Shale Surraée = ~——106— ! 
Warer Surfacé_._--.---—~\\2--~ | 
LEH. / j 
SCALE OF FEET 
100 50 0 100 200 
Fic. 4.—Four-acre tract near Canon City, Colo., showing plan of drainage. 
The shale is comparatively soft, from dark blue to reddish brown in 
color, and carries considerable water. The water apparently comes 
from the north, following along the joints in the shale strata, 
although it is believed that the extreme wet condition of the north- 
west corner is due in part to the movement of the water in the top 
soil from the tract to the west, which also is very wet. The under- 
lying shale ridges on this tract are not well defined; they are broad 
and flat. A rather broad shale ridge comes in at the northwest 
