10 BULLETIN 835, TJ. S. DEPARTMENT OF AGRICULTURE. 



soil with the same percentage of water used in different boxes 

 received the same amount of tamping. 



MEASURING THE ADVANCE OF MOISTURE. 



The change in color of the soil in the dry part of the column with 

 a change in moisture content was very marked in nearly all soils ex- 

 cept the light sands, devoid of much organic matter. With the posi- 

 tion of the contact of the wet and dry part of the column at the 

 commencement of the experiment marked upon the glass side of 

 the box, it was a simple matter to measure the distance the moisture 

 had moved into the dry part of the column at any time. These 

 measurements were recorded, as well as the date and hour of the 

 measurement. 



OTHER OBSERVATIONS OF THE SOIL COLUMN. 



During an experiment and at its expiration close observations were 

 made of the condition of the column for cracks or other factors that 

 might influence the ultimate results. At the end of the experiment 

 observations were made at the outer extremity of the apparent wetted 

 area in the original dry part of the box to determine if the advance of 

 the moisture had been the same in all parts of the column. In many 

 cases it was found that the extent of the movement was a little- 

 greater upon one side of the column than upon the other. These 

 differences were probably caused by differences in temperature rather 

 than lack of uniformity in packing. 



PROTECTION FROM SUN AND RAIN. 



To protect the flumes from the direct rays of the sun and from the 

 rain, canvas covers were provided. These covers were held away 

 from the sides of the flumes and from the top by iron bows and iron 

 strips similar to the old-fashioned wagon cover. This provided 

 ready circulation of air and ample protection from the weather. 

 Inasmuch as each flume was protected in this way no corrections had 

 to be made for the exposure of the flumes to the sun's rays due to 

 differences in angles of inclination or their setting in reference to the 

 compass. Figure 1 shows the tank ell or wick and a section of flume 

 as they appear when in position for filling. 



THE TANKS. 



The tanks used to contain the water from which the soil columns 

 obtain moisture are made of galvanized iron. They are 12 b} r 20 

 inches in area and 8 inches deep. Near the bottom and at one end 

 of each tank is fitted a §-inch water-gage glass, extending upward 

 upon the outside of the tank, so that the height of the water in the 



