734 EXPERIMENT STATION RECORD. 



surface tension of the soil moisture is kept very low and could be only slightly influ- 

 enced by the addition of salts. The application of substances to the soil for the 

 purpose of changing its water content through a change in the surface tension 

 would not, therefore, necessarily be productive of marked results. 



"If we take the viscosity ' of water at 0° C. to be 100, the viscosity at 25° C. is 50, 

 at 30° is 45, and at 50° about 31. This great variation in viscosity with change of 

 temperature is illustrated in the flow of water through soils which King 2 found in 

 his leaching experiments but failed to explain. 



"The viscosity of gases in opposition to that of fluids increases with increase of 

 temperature. Air, which is largely used in making so-called 'permeability' deter- 

 minations of soils, has a viscosity of 0.00017 (14.00273 t). An increase in tempera- 

 ture of 40° C. would therefore cause the coefficient of viscosity of air to increase one- 

 tenth of its amount. This evidently should always be taken into consideration in 

 determining the physical character of a soil." 



Little is definitely known of the nature of the film which constitutes 

 the hygroscopic moisture, and the author proposes to study the subject 

 later. 



"The one important factor which determines the acquirement aud retention of soil 

 moisture is the curvature of the capillary water surfaces. If equal volumes of 2 soils 

 are placed in contact, and the curvature of the snrface is less in the first than in the 

 second, then water will move from the first to the second, increasing the curvature 

 in one and decreasing it in the other until it becomes the same in both soils. If the 

 second soil contains a greater number of capillary spaces than the first, it will con- 

 tain more water when equilibrium is established. During the adjustment water will 

 have actually moved from a soil containing a low percentage of water to one having 

 a higher percentage. In no case, however, will water leave a capillary space having 

 a water surface of large curvature to go to a space with a surface of less curvature. 

 It is the form of the surface which determines the movement of the water." 



Investigations on the temperature conditions of different kinds 

 of soil, E. Wollny (Forsch. Agr. Phys. [ Wollny], 20 {1897), No. 1, pp. 

 133-186). — This is a second contribution to this subject. 3 The previous 

 paper related to the temperature conditions of humus, clay, and quartz- 

 sand soils. The present article is devoted to the temperature condi- 

 tions in calcareous, magnesian, and ferruginous soils, as determined 

 by observations extending over a number of years. The results are 

 reported in detail and indicate that calcareous and magnesian soils 

 have a decidedly lower heating and cooling capacity than other mine- 

 ral soils; i. e., they are colder during warm periods and warmer during 

 cold periods. The variations in temperature are also smaller in these 

 soils than in others of mineral origin. As regards the influence of 

 different forms of lime and magnesia, the results indicate that during 

 the warmer half of the year soils containing gypsum are, as a rule, the 

 warmest; those containing calcium carbonate standing next, and those 

 containing magnesium carbonate being the coldest. The variations in 

 temperature are smallest for the gypsum soil aud greatest for the cal- 

 cium carbonate soil. Crystallized calcium carbonate showed a greater 



1 Smithsonian Physical Tables, 1896, p. 136. 



2 U. S. Dept. Agr., Weather Bureau Bui. No. 5, p. 66. 



3 Forsch. Agr. Phys. [Wollny], 19 (1896), p. 305 (E. S. 11., 8, p. 964). 



