14 BULLETIN 835, U. S. DEPARTMENT OF AGRICULTURE. 



In so far as the writer knows, there is very little knowledge of 

 the quantitative effect of these different factors upon the movement of. 

 soil moisture, general information being limited to the fact that they - 

 do influence the movement. There are a few data upon the quanti- 

 tative effect of temperature (2) and some of the other meteorological 

 factors and also of the soluble salts (3), but they are incomplete and 

 in some instances confusing. In the experiments herein discussed, the 

 evaporation factor has been controlled and taken into account within 

 certain limits, and the results of this work will be discussed later in 

 the report. 



In any comparison of the data from one soil with the data ob- 

 tained from a different soil none of these factors has been taken into 

 account. Chemical and mechanical, analyses of the soil can be ob- 

 tained readily, but with our present knowledge such information 

 would be of no service in making quantitative comparisons. For in- 

 stance : The colloids influence the movement of capillary moisture in 

 one way, while the organic material, as indicated by the organic car- 

 bon, exerts an influence in the opposite direction, There is not suffi- 

 cient information to indicate in the least to what extent these two 

 factors might compensate, if at all. Other factors tend to retard the 

 movement of the moisture, while others, again, tend to augment it. 

 but to what extent our present information does not indicate. 



The experiments herein recorded were run at various times 

 throughout the year and in the open. Some of the soils were tested 

 during the heat of August and others during the cold weather in 

 January. Others of the soils were tested at a time when they en- 

 countered periods of almost extreme heat and extreme cold. It is 

 known with reasonable certainty that the rate and extent of move- 

 ment of soil moisture is greater with temperature above but near the 

 freezing point than at a higher temperature. That a temperature of 

 from 26° to 32° F. has a marked influence upon soil moisture other 

 than the mere fact of freezing will be indicated by data presented 

 later in this report. 



In the data herein presented, no corrections are attempted for 

 temperature or other factors unless specifically stated. It must be 

 kept in mind that in the calculations for comparison and in the 

 derivation of formulae the conclusions reached are applicable only 

 to the soil under consideration and under the same conditions. 



MOVEMENT OF MOISTURE IN VERTICAL TUBES FROM FREE WATERS. 



The experiments herein recorded differ from other work that has 

 been done in vertical tubes only in that the tubes are larger and the 

 work has been carried to a greater extent (3), (12). (13), (14). 

 These tubes or flumes have also been subjected to variations of tern- 



