134 THE ROYAL SOCIETY OF CANADA 



indicated that the above theory is true for a heavy clay subsoil. It 

 acts as a semi-permeable membrane ; its efficiency as a semi-permeable 

 membrane increases with its depth ; and the soil moisture moves through 

 the soil membrane from points of less concentration to points of 

 greater concentration. 



In 1913 I had the honor of reading a paper 1 before this society 

 in which I gave some results obtained by using the soil constituents 

 as semi-permeable membranes. In the mechanical analysis of soils, 

 the soils are divided into grades according to the size of soil particles. 

 The grades are known as sands, silt and clay. These are the soil 

 constituents. 



We found that the smaller the soil particles in a soil constituent 

 the greater is .the efficiency of the constituent as a semi-permeable 

 membrane. 



In the papers read in 1912 the greatest osmotic pressure recorded 

 was 5-6 grams per square centimeter. This corresponds to a water 

 column about 2 inches high. 



In the paper read beofre this society in 1913 the greatest osmotic 

 pressure recorded was 42 • 5 grams per square centimeter, correspond- 

 ing to a water column about 16 inches high. 



This year we have carried this further and we have obtained, 

 as is shown below, an osmotic pressure of 352 grams per square centi- 

 meter corresponding to a water column of over 11-5 feet. 



Part I. 



On the Osmotic pressure obtained by using a column of very fine soil us a semi- 

 permeable membrane, and a concentrated soil solution as the active solution. 



How the Soil Was Prepared. 



We used a loam soil which we knew contained a considerable 

 amount of very fine soil. The loam was soaked in bulk over night in a 

 pan of distilled water. From this mud eight shaker bottles were 

 loaded each with approximately, 5 g. of soil, 150 c.c. distilled water 

 and 5 drops of ammonia. 



After one hour in the shaker the bottles were allowed to stand 

 for 15 minutes and the liquid was decanted into an enamelled pan 

 which was then placed in an oven at 110°C. A further 150 c.c. of 

 distilled water was then added to each bottle and the bottles were 

 again shaken for 1 hour. After standing for 15 minutes the liquid 

 was again decanted and added to the liquid obtained from the first 

 shaking. To sterilize the liquid and free it from ammonia it was 



1 "On Osmosis in Soils." Translations of the Royal Society of Canada, Third 

 series, Vol. VII (1913). 



