568 



SCIENCE. 



[N. S. Vol. XX. No. 513. 



urements consequently serve to indicate the 

 variation in the concentration of the soil solu- 

 tion. The fourth column gives the moisture 

 content of the surrounding soil taken at a 

 distance of from twelve to fifteen inches from 

 the tube. These determinations are rather 

 unsatisfactory, since it was not possible to 

 obtain the samples at a uniform distance from 

 the tube, and the moisture determinations are, 

 therefore, not strictly comparable. 



Soil Moisture Removed by Abtiticial Root. 



The soil in which these experiments were 

 made had been heavily fertilized the previous 

 year. It will be noted that the conductivity, 

 which we may assume as approximately pro- 

 portional to the salt content, steadily increased 

 from the beginning of the observations, June 

 Y until June 18. The rain on June 21 appar- 

 ently did not change the concentration of the 

 solution. After the rain on July 1, the 

 conductivity dropped from 89 to 83, after 

 which it steadily increased until the next rain 

 on July 7. From that time, the conductivity 

 increased from 81 to 91 on July 16. The 

 rain on the latter date did not change the 

 conductivity, due, perhaps, to an accumula- 

 tion of soluble material at the surface as the 

 result of evaporation on the preceding days. 



which was carried down by the rain. The 

 maximum increase in the electrical conduc- 

 tivity of the soil solution, taking the initial 

 value as a basis of comparison, amounted to 

 about 21 per cent. The increase in the total 

 solids, determined gravimetrically by evaporat- 

 ing a given volume of the soil solution to 

 dryness, was about 32 per cent., the total solids 

 varying from 1.6 gms. to 2.1 gms. per liter of 

 solution. The maxima in the curves, repre- 

 senting the variation in the electrical conduc- 

 tivity and total solids in the soil solution, do 

 not always correspond, which indicates a 

 change in the composition of the solution as 

 well as in the concentration. 



The rate of translocation of the soil moisture 

 into the tube, at the beginning of the experi- 

 ment, after a heavy rain, was 8.9 grams per 

 hour. It fell steadily during the next two 

 weeks to about 1 gram per hour. Heavy rains 

 in July 1 brought the rate up to an average of 

 13.Y grams per hour for the twenty-four hour 

 period, after which it fell to 1.5 grams per 

 hour on July 7, and so on. 



The rates given represent, of course, the 

 average rate for the period. At the time of 

 a shower, the rate would temporarily be much 

 greater. The apparatus is amply able to re- 

 move the water as fast as it can be supplied. 

 A tube in good condition, when immersed in 

 water and exhausted, will take up water at the 

 rate of 50 grams per minute, while the great- 

 est rate recorded in the table is only about one 

 two-hundred-and-fiftieth as fast. 



The apparatus thus provides : 



(1) A means of determining the rate at 

 which water can be supplied by a soil to an 

 artificial root, by means of which a capillary 

 pull is exerted upon the soil moisture of any 

 desired magnitude up to one kilogram per 

 sq. em. This makes possible the comparison 

 of rates of capillary movement in different 

 soils under field conditions. 



1;^2) A simple method of removing a portion 

 of soil moisture with the dissolved substances 

 which it contains, thereby enabling a study 

 of the concentration and composition of the 

 soil solution under different field conditions. 



This apparatus has the disadvantage of being 

 able to remove water from the soil only when 



