78 THE ROYAL SOCIETY OF CANADA 



In this connection it must be stated that the electrical resistances 

 were taken near the top of the tubes in all cases except when distilled 

 water was used. In this case it was taken near the bottom of the tube. 

 Had the other resistances been taken at this point it is probable that 

 they would have been lower. 



(3) At low concentrations the flow decreases very slowly with 

 decreasing concentration and there is still a marked flow when dis- 

 tilled water is used instead of soil solution. This was investigated 

 in the eighth test. 



EIGHTH TEST. WHY IS THERE A FLOW WHEN DISTILLED WATER IS 

 USED AS THE SOLUTION ? 



It seemed remarkable that a flow should take place with distilled 

 water inside and outside the tube. The following explanation occurred 

 to us and when tested seemed to be correct. 



The explanation is as follows. That part of the distilled water 

 in the tube which is in contact with the soil forms a soil solution and 

 this solution on account of its density remains in contact with the soil. 

 That part of the distilled water in the bottle which is in contact with 

 the soil forms a solution and this solution on account of its density 

 sinks to the bottom of the bottle and is replaced by fresh distilled 

 water. Thus the liquid just above the soil is a soil solution and the 

 liquid just beneath the soil is nearly pure distilled water, and the 

 flow takes place from the water to the solution. 



To test this explanation we filled the tubes, used in the seventh 

 test, with fresh distilled water and placed them in small test tubes 

 containing distilled water. The bottoms of the tubes were almost 

 in contact with the bottoms of the test tubes. 



Our reasoning was that if the solutions inside and outside the 

 tube had the same concentration there would be no flow, but if they 

 had different concentration there would be a flow in the direction of 

 the stronger solution. In the experiment the outside solutions be- 

 came more concentrated than the inside solutions and the flow was 

 toward the outer solutions. 



