4 BULLETIN 30, U. S. DEPARTMENT OF AGRICULTURE. 



face ; and (5) temperature, especially the frequency of killing frosts 

 which limit the growing period. These factors will be discussed as 

 they have been recorded * at the Nephi substation. Figure 2 shows 

 the apparatus used in recording these data. 



Fig. 3.— View of one wall of a deep gully or small canyon near the Nephi substation, showing stratified 

 soil formation to a depth of 20 feet. The light-colored stratum is the blue clay mentioned in the 

 text. 



son,. 



The soil of the Nephi substation is reasonably typical of a large 

 proportion of the soils of the Great Basin, which are mostly alluvial. 



1 With the exception of the rain gauge, the physical apparatus inuseat the substation was installed by 

 the Biophysical Laboratory of the Bureau of Plant Industry, which is cooperating in the work. The 

 apparatus includes an evaporation tank, an anemometer, an air thermograph, thermometers, psychrom- 

 etcrs, and a complete outfit for making soil-moisture determinations. 



