the land is but little more than 20 inches. If this
water fell upon a flat surface of soil, with an impervious subsoil of
rock or clay, we should have some sixteen inches of water in the course
of the year more than evaporates from the land. If a given field be
dish-shaped, so as to retain it all, it must become a pond, and so
remain, except in Summer, when greater evaporation from a water surface
may reduce it to a swamp or marsh.

With 16 or 18 inches more water falling annually on all our cultivated
fields than goes off by evaporation, is it not wise to inquire by what
process of Nature or art this vast surplus shall escape?

Experiments have been made with a view to determine the proportion of
evaporation and filtration, upon well-drained land, in different months.
From an able article in the N. Y. Agricultural Society for 1854, by
George Geddes, we copy the following statement of valuable observations
upon these points.

It will be observed that, in the different observations collected in
this chapter, results are somewhat various. They have been brought
together for comparison, and will be found sufficiently uniform for all
practical purposes in the matter of drainage.

"The experiments upon evaporation and drainage, made on Mr.
Dalton's plan, were in vessels three feet deep, filled with soil
just in the condition to secure perfect freedom from excess of
water, and the drainage was determined by the amount of water that
passed out of the tube at the bottom. These experiments have been
most perfectly made in England by Mr. John Dickinson. The following
table exhibits the mean of eight years:

======================================================================
YEAR.| October to March. || April to September.|| Total each year.
-----|--------------------||--------------------||--------------------
|Rain.|Filtra-| [%] ||Rain.|Filtra-| [%] ||Rain.|Filtra-| [%]
| | tion. | || | tion. | || | tion. |
-----|--------------------||--------------------||--------------------
1836 |18.80| 15.55 | 82.7 ||12.20| 2.10 | 17.3 ||31.00| 17.65 | 56.9
1837 |11.30| 6.85 | 60.6 || 9.80| 0.10 | 1.0 ||21.10| 6.95 | 32.9
1838 |12.32| 8.45 | 68.8 ||10.81| 0.12 | 1.2 ||23.13| 8.57 | 37.0
1839 |13.87| 12.31 | 88.2 ||17.41| 2.60 | 15.0 ||31.28| 14.91 | 47.6
1840 |11.76| 8.19 | 69.6 || 9.68| 0.00 | 0.0 ||21.44| 8