278 NATURE AND PROPERTIES OP SOILS 



Anotlier device, perfected by Briggs and McCall,^ consists 

 of a close-grained, nnglazed porcelain tube, closed at one end 

 and provided at the other with a tnbulnre, by which it can 

 be connected with an exhausted receiver. This tube is mois- 

 tened and buried in the soil. If the moisture content of the 

 soil is sufficient to reduce the pressure of the capillary water 

 surface in the soil to less than half the difference between the 

 pressure inside and outside of the tube, there will be a move- 

 ment of water inward. The water may be collected and ana- 

 lyzed. 



More recently Van Suchtelen has used another method to 

 obtain the soil solution.^ He replaces the soil-water by means 

 of paraffin in a liquid state, at the same time subjecting the 

 soil on a filter to suction. The displaced water is considered 

 to represent the soil solution. Later Van Suchtelen and Itano 

 substituted pressure for suction, modifying the apparatus to 

 meet the new procedure. This apparatus has been further 

 perfected by Morgan.^ Lipman ^ has proposed a method in 

 which very high pressure, a minimum of 53,000 pounds to the 

 square inch, is utilized in squeezing out the soil-water.^ 



All such methods are open to the objection that the sample 

 is not representative. The soil solution changes both in con- 



^Briggs, L. J., and MeCall, A. G-., An Artificial Boot for Inducing 

 Capillary Movement of Soil Moisture; Science, N. S., Vol. 20, pp. 

 566-569, 1904. 



^Van Suchtelen, F. H. H., Methode zur Geivinnung der Natiirliclien 

 Bodenloswng ; Jour. f. Landw., Band 60, Seite 369-370, 1912. 



^Morgan, J. F., Tlie Soil Solution Oltained hy the Oil Pressure 

 Method; Mich. Agr. Exp. Sta., Tech. Bui. 28, Oct., 1916. 



* Lipman, C. B._, A New Method of 'Extracting the Soil Solution; Univ. 

 Cal. Pub., Agr. Bel, Vol. 3, ISTo. 7, pp. 131-134, 1918. Bamann, B., et al, 

 have proposed a similar method but with less pressure. Internat. Mit. f. 

 Bodenkunde, Bd. 6, Seite 27, 1916. 



For a good criticism of this method, see Northrup, Zea, Science, 

 K S., Vol. XLVII, No. 1226, p. 638, June 1918. 



^Ischerekov in 1907 used ethyl alcohol to displace the water in a 

 soil column utilizing only the force of gravity. Parker claims that 

 this method is of considerable value. He found that data so obtained 

 compared closely with that obtained from the water extract method. 

 Parker, F, W., Methods of Studying the Concentration of the Soil 

 Solution; Soil Sci., Vol. XII, No. 3, pp. 209-232, 1921. 



