72 



THE ROYAL SOCIETY OF CANADA 



FIRST TEST. IS THE FINAL PRESSURE CONSTANT UNDER 

 GIVEN CONDITIONS ? 



The theory on which we have been working is as follows: It is 

 possible (1) that soils act as partial semi-permeable membranes (2) 

 that water moves through the soil by osmosis. 



If this theory is true and if we have tubes set up as in Fig. 1, the 

 final pressure produced should be the same whether the solution in the 

 measuring tubes is started at the water level and allowed to rise or 

 is started at the top of the measuring tubes and allowed to fall. This, 

 on trial, proved to be the case. 



Four tubes were set up as in Fig. 1. The liquid in the four 

 measuring tubes was started, first at zero; next at a pressure of 42-4 

 cms. of water and lastly again at zero. The final pressures were 

 obtained in each case in about two weeks but the tubes were allowed 

 to stand one week longer to make sure. 



Table I. 



Giving the Final Pressure in Centimetres of Water, obtained 

 IN EACH Tube. 



Conclusion. The final pressure is approximately constant. 



SECOND TEST. IS A FLOW PRODUCED ? 



If the soil does act as a semi-permeable membrane and if the water 

 does move through the soil toward a solution of higher salt content, 

 then if the apparatus is arranged as in Fig. 2, there should be a flow 

 of the solution along the horizontal measuring tubes, and since with 

 the apparatus arranged in this way the maximum pressure cannot 

 be produced, the flow should continue as long as the solution in the 

 tubes has a higher salt content than the water outside, unless the soil 

 is altered by the passage of water through it. The results indicate 

 that this is the case. 



The four tubes used in the first test were arranged as shown in 

 Fig. 2, the soil solutions being retained in the tubes. Daily observa- 



