MOVEMENT OF VARIOUS SALTS 147 



field soil, while in the deeper layers sodium bicarbonate 

 and sodium carbonate gradually replaced the former salts. 

 The work of Mackie (24) in California indicated that 

 sodium carbonate was readily absoibed by the soils and 

 therefore held its position in the soil well. On irrigated 

 soils he usually found sodium carbonate' in the greatest 

 quantities near the surface, but on virgin soil its location 

 varied in depth down to the hardpan. From results on 



/ ' ' :.& 



FIG. 18. ALKALI EATING AWAY THE FENCE POSTS. 



land irrigated 4 or 5 years presented by Hilgard and 

 Loughridge (16) it appears that sodium chloride moved 

 upward to the first foot relatively faster than sodium sul- 

 phate and considerably faster than sodium carbonate. 



Few data are at hand to show to what extent this dif- 

 ference in the rate of movement of the different salts pro- 

 ceeds under field conditions. Analyses of drainage water 

 from alkali land near Salt Lake City, Utah, reported by 

 Dorsey (6) show that in the course of three years the 

 chloride was removed relatively faster than the other 

 alkali salts when it constituted by far the greater part of 



