506 



STATE BOARD OF AGRICULTURE. 



packed, or unevenly packed, there will be left an easy channel for the 

 displacing liquid to pass without much pressure being exerted and also 

 without obtaining the total amount of solution possible. The pressure 

 exerted will depend upon the moisture content of the soil. It is raised 

 gradually as long as moisture continues to come until finally 500 lbs. 

 pressure is used if the oil has not come through before the pressure 

 reaches this maximum. One reason why the pressure is raised grad- 

 ually is to give the soil an opportunity to adjust itself and thus to pre- 



PLATB 1. BATTERY OF 3 CYLINDERS SET UP FOR USB SHOWING THE MANNER 

 OF CONNECTION, GAGE AND PUMP AND ALSO THE WAY THE SOLUTIONS WERE 

 COLLECTED. 



vent the oil from coming through too soon due to the formation of chan- 

 nels. Some soils with a very high moisture content will, even on pack- 

 ing, give off some of the solution that tliey contain. 



When the oil comes through in any of the cylinders, the valves on the 

 others are closed to hold the pressure attained, while the pressure is be- 

 ing released on the first by opening the release valve on the pump. After 

 this, the operation is reversed and the pumping is continued as before. 

 When all the cylinders are used for extraction of the same soil, all ex- 

 tractions, if mixed, will give an abundance of material to work with. In 

 the sandy soils, oil will make its appearance generally from 3 to 9 

 hours, while with the finer grained soils the oil may not come through 



