DISCUSSION OF MOISTURE' DETERMINATIONS. 



Conditions found April 12, iSgy. 



Since the capacity of a soil to hold water depends upon its 

 fineness, the maximum water capacity will, other things being 

 equal, vary inversely as with the size of the soil particles. Also, 

 the coarser a soil, the heavier a given dry quantity of it is, as a 

 rule. Hence, as is to be expected, it will be observed that the 

 maximum water capacity percentages vary inversely as the 

 weights per cubic foot, in most cases. For example, the foot 

 composed of the coarsest matter — the seventh — was the heaviest, 

 and was capable of holding the least water ; while the higher per- 

 centages of water capacity are found in the soils that are the 

 lightest when dry. 



That the ability of a soil to retain water depends upon its 

 fineness also, is well illustrated by the determinations given in 

 Table I. During even the two weeks intervening between the 

 last irrigation of the winter, in 1899, and the taking of the 

 samples March 12th, the gravel had evidently lost a much great- 

 er percentage of the water it, was capable of holding than the 

 finer soil above and below it. The absence of water in gravel 

 lying next to fine clay is especially noticeable. In the case of 

 the stratum of gravel between the 14th and 16th foot, the degree 

 of saturation was very different from that of the strata on either 

 side, causing the turns in the moisture lines in Figs. 7 and 8, as 

 will be seen, to be very abrupt. It would seem that the finer 

 soils acted like a sponge in absorbing the moisture from the 

 coarser ones. The determinations given could not be explained 

 on the ground of percolation alone, for if only the latter were tak- 

 ing place, in the samples taken March 12th, the gravel just above 

 the clayey 14th foot for example, would be moister than that far- 

 ther above. 



When the fine soil below the 15th foot is reached the changes 

 in moisture from foot to foot are more gradual and regular. The 

 clay just below the stratum of gravel was very wet at the time of 

 taking the first set of samples, April 12th, 1899, due evidently to 

 the fact that it had received water from the gravel above more 



