18 T. Lyttleton Lyon and James A. Bizzell 



was driven under each one to form a bottom. The soil therefore has 

 not been greatly disturbed. It is a rather heavy loam and is kept free 

 of vegetation. There are three lysimeters, representing depths of 20, 

 40, and 60 inches, and for the twenty-four years from September, 1877, 

 to August, 1901, the percolation according to Miller (1903)- was, 

 respectively, 50, 53.2, and 50.1 per cent of the rainfall. The maximum 

 and the minimum drainage occur, respectively, in November and in June. 



Four years later Miller (1906) again reported on the flow from these 

 lysimeters, and included the records from 1870, when the gauges were 

 installed, up to 1905, a period of thirty-five years. The average rainfall 

 for the period was 28.97 inches, of which 47.8 per cent passed thru the 

 20-inch gauge, 50.4 per cent thru the 40-inch gauge, and 47.1 per cent 

 thru the 60-inch gauge. The fall and winter months show the greatest 

 percolation, and the summer months the least. This is true of the per- 

 centage percolation as well as the absolute. 



An early report on the drainage from the Rothamsted lysimeters was 

 made by Gilbert (1876), whose figures indicate that from September, 

 1870, to August, 1875, inclusive, the average annual rainfall was 27.93 

 inches, of which 36.8 per cent passed thru the 20-inch gauge, 36 per cent 

 thru the 40-inch gauge, and 28.6 per cent thru the 60-inch gauge. A com- 

 parison of the observations made by Gilbert with those of Miller lead to the 

 conclusion that the percentage percolation, as well as the al)solute, increased 

 very materially after the first five years. It is a common observation 

 that tile drains in heavy soil run more freely after they have been in 

 operation for a few years. 



The more recent European experiments dealing with the proportion 

 of rainfall that percolates thru the soil, may be considered to have begun 

 with those of Wollny (1888) at Munich, Germany. He reviews the 

 previous work on this subject, which is here summarized in table 7. 



By means of metal lysimeters Wollny studied the effect of certain 

 physical conditions of the soil on percolation. He used cylinders of two 

 sizes. The smaller cylinders had an area of 400 square centimeters 

 and were 30 centimeters deep; the larger ones were 1000 square centi- 

 meters in area and had a depth of 50 centimeters. In some of his experi- 

 ments he used soil, and in others he used quartz sand of different degrees 



2 Dates ia parenthesis refer to bibliography, pages 82-84. 



i8 



