12 
Journal of Agricultural Research 
Vol. XXVI, No. T 
MINUTES 
Fig. i.—C urve i, soil from a California orange grove, showing low swelling coefficient and auxotaxic curve 
with one stage. Thickness of io-gm. disk, 5.82 mm. Curve 2, soil from the experiment station, Salt 
River Valley Farm, showing moderate but very rapid swelling in two stages; xo-gm. disk, 5.72 mm. 
Magnified 10X. Vertical scale in centimeters. 
MINUTES 
Fig. 2.—Curve 3, a silty clay recently deposited by the Rillito River near Tucson, containing a small amount 
of organic matter; 10-gm. disk, 5.68 mm. Curve 4, a black loam from near Tucson, showing two swelling 
stages of different rate; 10-gm. disk, 5.63 mm. Curve 5, a calcareous clay recently deposited by the: 
Gila River; 10-gm. disk, 5.98 mm. Magnified 5X. Vertical scale in centimeters. 
MINUTES 
Fig. 3.—Curve 6, a calcareous clay from Utah that crushed drain tiles laterally, expanded in distilled water 
at 27°C.; 10-gm. disk, 5.58mm. Curve 7, same, expanded in distilled water at 0° C.; 10-gm, disk, 5.61 mm- 
Curve 8, same, expanded in distilled water at 70° C.; 10-gm. disk, 5.61 mm. Curve 9, same, expanded in 
1 per cent sodium chlorid solution at 27° C.; 10-gm. disk, 5.63 mm. Magnified 5X. Vertical scale in 
centimeters. 
•Fig. 4. —Curve 10, a calcareous, black alkaline loam very low in organic matter, from Casa Grande Valley „ 
expanded in distilled water at 27 0 C.; 10-gm. disk, 5.78 mm. Curve 11, same, expanded in 1 per cent 
sodium chlorid solution at 27 0 C.; 10-gm. disk, 5.76 mm. Magnified 5X. Vertical scale in centimeters. 
