OF SOUTH CAROLINA. 251 
“Highland Agricultural Society,” of Scotland, in which was given the result of numerous experi- 
ments, illustrative of the subject—from which it appears, 
1. That excess of stagnant water in the soil prevents the free access of atmospheric air, which 
has been shown to be necessary to the fertility of the soil. On the contrary, when the water has 
a free outlet through the soil into the drain, every shower of rain displaces the water in the soil, 
which is followed by atmospheric air, and a healthy downward current of water and air is estab- 
lished, instead of an upward one of stagnant water, produced by evaporation. 
2. The temperature of an undrained soil is greatly diminished, as compared with one well 
drained—the difference amounting to 64° Fahr. in experiments continued for several days. 
In winter a drained soil will assume the temperature of the atmosphere, but in an undrained, the 
temperature will remain at between 39° and 40°, owing to the fact that water has its greatest 
density at that temperature, and hence increase of heat or cold causes it to become lighter—so that 
in either case, there is no transmission of particles downwards, after this temperature has been 
attained, and consequently no decrease of temperature, and the relation between the temperature of 
the air and the soil, so necessary to vegetation, is deranged. 
3. The effects of excess of water in the soil, on the results of the decomposition of organic 
matter, has been already alluded to. Instead of the highly nitrogenized substance into which 
vegetable matter is converted, when decomposed in the air, or in a porous and properly drained soil, 
there is left a black inert matter. Besides, as oxygen is necessary to decomposition, and all the air 
present in an undrained soil is that dissolved in the water, it can derive but little from that souree— 
it must take it from the water itself. Hydrogen is therefore set free, which unites with the carbon, 
forming carbonetted hydrogen, which takes away a portion of carbon from the soil, if it be not 
even injurious to the growing plants. Ina well drained soil pervaded by atmospheric air, the 
hydrogen set free might have united with nitrogen to form amonia. 
4. The evaporation going on from a wet soil keeps the growing plants constantly in a damp 
atmosphere, thereby retarding the healthy exhalation from the surface of the leaves, so necessary 
to their healthy growth. 
5. But perhaps the most interesting effects of drainage are the influences exerted on the chemi- 
cal changes going on among the salts in the soil. 
Bertholet had, long ago, shown the modifications to which affinity is subject, dependent upon the 
circumstances under which matter may be placed. For instance, if carbonate of lime and muriate 
of soda, (common salt,) be brought together with excess of water, no chemical change can take 
place; if, however, they be barely moistened, decomposition commences, and two new salts, muri- 
ate of lime and carbonate of soda, are formed. They are both soluble, and highly valuable—the 
carbonate of soda increasing the solubility of the organic matter in the soil, and the other increas- 
ing its absorbent and retentive powers. If excess of moisture be again present, these salts return to 
their original state. 
If a mixture be made of sulphate of lime and carbonate of amonia, and moistened or mixed with 
moist sand, so as to represent the state in which a well drained soil exists, an interchange takes 
place, and sulphate of amonia and carbonate of lime are formed. Now by this process the volatile 
carbonate of amonia is fixed and retained in the soil. This is the basis of Leibig’s theory of the 
fixation of amonia by sulphate of lime, or gypsum. 
