24 T. Lyttleton Lyon and James A. Bizzell 



These results show great differences, for which it is difficult to account. 

 The lowest and the highest percentage percolation for bare soil are 10.5 

 and 107, respectively. The lowest percolation was in a region of good 

 rainfall but great evaporation. The highest was with a light rainfall 

 and probably what would be a moderate rate of evaporation; this was 

 one of Ebermayer's experiments, and as the percolation in this case was 

 greater than the rainfall the result is of doubtful accuracy. 



It is noticeable that one of the experiments giving the highest percentage 

 percolation was conducted with tile drains over a large area. 



The percolation thru bare soil in the lysimeters at Gottingen agree 

 very closely with those at Rothamsted, the rainfall being about the same 

 at the two places. The summers are probably a little warmer at Gottingen, 

 the winters a little colder, and the atmospheric humidity somewhat less 

 at all times. These differences, however, are not great as compared 

 with some of the other climates represented by the experiments. 



At Cawnpore, India, the percentage percolation is less than at the 

 two places just mentioned, and this is to be expected in a hot climate 

 such as that of India, even tho the rainfall is greater. 



The same is the case to a greater extent at College Station, Texas, 

 where the rainfall is slightly greater than at Cawnpore, but the rate of 

 evaporation is probably greater. 



At Jonkoping, with its shorter summer and consequently decreased 

 annual evaporation, the percolation is greater than at Rothamsted. 

 At Ithaca the percolation is even greater than at Jonkoping, altho the 

 annual evaporation is probably greater. There are other factors that 

 may contribute to this. At Ithaca there are several months each year 

 when the ground is frozen and when evaporation is nil. In the spring 

 comes a thaw, which begins at the bottom of the frozen soil and gradually 

 approaches the surface, during which time drainage takes place freely. 

 The process of thawing causes the soil to become friable and this still 

 further aids the drainage process. The result is that a very large pro- 

 portion of the drainage occurs between the first of January and the end 

 of April, while at Rothamsted the greatest drainage appears to occur 

 in the autumn due to the fact that there is little freezing of the soil to 

 facilitate the rapid carrying-off of the excess water in the early spring 

 before conditions are favorable for evaporation. 



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