THE PHYSICAL ACTION OF LIME ON CLAY SOILS 



17 



tent. In order to observe expansions under these conditions, a series 

 which was running for 100 days was selected for special experimenta- 

 tion. Measurements were made according to a method suggested by 

 Professor J. A. Bizzell of Cornell University. A ratchet micrometer was 

 fastened to a standard so that the spindle head could play on a brass 

 pin which projected three-fourths of an inch above the surface of the 

 soil. The pin passed perpendicularly through the middle of a small brass 

 plate, the latter resting on the soil surface. The pin was further steadied 

 by a projection passing down into the soil. A reading was made by 

 lowering the micrometer spindle gently in to the pin, until there was 

 a constant "pull" on the slip of thin paper inserted between pin and 

 spindle. This method is accurate to the hundredth of a millimeter. 



In setting up the experiment, pins were placed on the one-half, one 

 and one-half, and ten ton treatments only. The initial reading was 

 made three hours after the pots had been brought up to weight. During 

 the course of the experiment readings were taken from time to time; 

 in each case, however, 24 hours after watering, inasmuch as approxi- 

 mately 24 hours were required to evaporate the water from the quartz 

 mulch. 



EFFECT OF TIME AND SALTS ON SOIL EXPANSIONS 



(Each figure in the following data is the average of quadruplicate determinations. 

 The values all have a negative sign, i. e., there was contraction in every case. 

 Readings are in mm.) 



