WATER — SOILS. 425 



"The height of the water jjlane often changes without sensihle cause, probably 

 due to atmospheric conditions, pressure,' temperature, etc. Light rains (hiring dry 

 periods produce, as a rule, comparatively great increases in the height of the water 

 plane, probably due to modification of the cajjillary conditions. Light rains during 

 an interval of abundant moisture when the soil is wet do not produce an increase in 

 the height of the water plane. Moderate rains were sometimes accompanied by tem- 

 porary depression of the water plane. This was accounted for l)y the rate of rain- 

 fall, character of soil, and the air contained therein. The effect of an irrigating ditch 

 running past the east end of the plat was to raise the height of the water plane by 

 0.3 ft. at a distance of 142 ft. from the center of the ditch. This rise was apparently 

 produced by the causing of a backward pressure and not by direct infiltration of 

 water. When the water plane rose due to changes in capillary conditions caused by 

 light rainfalls it usually fell to its former level in al>out 3 days, but when it rose after 

 an irrigation it required from 10 to 13 days for its fall. 



"The total solids, salts held in solution in the different well waters, varied both in 

 quantity and in the ratio of the different salts i^resent. Their amount and character 

 depended upon the conditions obtaining in the immediate vicinity of the well. The 

 total solids rose and fell with the water plane, passing into the water as it rose, and 

 remaining in the soil when it fell. . . . The increase in the amount of total solids in 

 a well water is not always the greatest in those wells which show the greatest rise in 

 the water plane, nor in those which usually show the greatest quantities of total sol- 

 ids. The increase in the total solids due to the rise of the water plane seems to be 

 partly dependent upon the rate of diffusion through the soil. . . . The total solids 

 in the well waters were less than in the water in the soil. This difference was not 

 dae to a mixture of water entering the wells from different sources, but was seem- 

 ingly due to the modification of the laws of diffusion and sf)lubility by the soil 

 itself. ... 



"The chlorin, or its corresponding salt, sodium chlorid, was at no time very 

 abundant in the ground water and bore no definite relation to the total solids, as the 

 sodium chlorid ranged from 5 to a little more than 14 per cent of their total weight. 

 The increase or decrease of sodium chlorid, conmion salt, was not proportional to 

 the increase or decrease of the total solids, and did not serve as an index of either 

 the amount of total solids present or of their variation, except within very wide 

 limits. The chlorin may not always be present in the form of sodium chlorid. . . . 

 Analytical results indicate that it may sometinies be jiresent as magnesium chlorid, 

 and the irregular deportment of chlorin in the waters may be due to such causes, 

 i. e., differences in the manner of its cond^ination. The chlorin present in the ground 

 waters and its variations in quantity throw but little or no light upon the movement 

 of the alkali salts within this soil. 



"The term 'total solids' is equivalent to the salts constituting the free solution in 

 the soil. The term represents a different mixture of salts than is found in the 

 incrustations forming on the surface of the soil, or obtained by evaporating an 

 aqueous extract of the soil to dryness. The total solids in the ground water varied 

 greatly in the different wells, and also from time to time, in regard to their quantity, 

 but only to a limited extent in their chemical composition. The difference in the 

 latter respect was almost exclusively confined to the relative quantities of the respec- 

 tive salts. . . . 



"The alkali incrustations from this plat consist essentially of sodium and mag- 

 nesium sulphate in the ratio of two to one. They together constitute 80 per cent of 

 the mass. Calcium sulphate is subordinate in quantity, M'ith sodium chlorid and 

 carbonate still more so. 



"The salts dissolved in the ground water, the total solids, consist nuich more 

 largely of calcium sulphate than of sodium sulphate, and contain about the same 

 amount of magnesium sulphate as the incrustation from this plat. The ratio of cal- 



