90 THE AMERICAN FARMER. 



together, is frozen, the clay particles, before so attenuated as to be invisible under the micro 

 scope, are precipitated in distinct flocky masses, which, under the microscope, transmit much 

 light and have a granular or cellular appearance ; and the water may be poured off quite clear 

 and free from milkiness. This result of freezing clay-water appears to be quite analogous to 

 that of freezing a thin starch paste, the starch being separated in glutinous clumps, and very 

 like the action of rennet or vinegar on milk, whereby the casein is coagulated or curdled. 

 Freezing thus coagulates clay, causes the swollen, gelatinous, transparent, clayey substance, so 

 retentive of water and so attenuated with water, to discharge the liqtRd and condense to a visi 

 bly flocky or granular matter. 



It is plain that tillage may modify the storage of water in the soil. If a compact clay or 

 loam be loosened in its texture, subsequent rains will more readily pass through the loosened 

 tilth and will penetrate and remain in reserve in the soil immediately underlying. This will 

 be advantageous in two ways. It will, first, give the sowed crop an aerated and therefore 

 healthy root-bed, and second, it will tend to conserve the rain against time of drought. 



On coarse-textured soils, deep and frequent tillage may too much promote the descent 

 of rain, and therefore be detrimental to vegetation. 



Let us now suppose the surface of the several soils we instanced, after being fully 

 charged with rain, to be equally exposed to the prolonged influence of sunshine and drying 

 winds, whereby the water at the surface and to a certain depth evaporates. At the very sur 

 face the soils all become quite dry. At some distance down they kept moist, because, as the 

 water escapes above, it is raised by capillary action. The larger the pores the deeper the soil 

 dries out, because the larger the pores the less does water rise in them. It will thus happen 

 that so long as there is water in the deeper layers of soil, so long the clay will remain moist 

 at almost the surface, while the quantity of moisture will decrease from soil to soil, in propor 

 tion to the coarseness of the pores, until in the gravel it may be dry almost throughout. 



That stratum of the soil which is subjected to loosening tillage is always dried thereby. 

 A wet soil sometimes may be advantageously plowed for the purpose of drying it. A dry 

 soil may be made too dry by deep and repeated tillage. The reasons are 1st. By loosen 

 ing, the soil is made to expose a vastly greater evaporating surface to the atmosphere than 

 the compact soil presents. 2d. The capillary connection of the loosened earth with the 

 underlying soil is impaired, and its power of taking up and distributing bottom-water is 

 diminished. 3d. The rain that falls upon it flows more freely and completely into the sub 

 soil. Thus its rate of losing water is increased, and the sources of supply are rendered less 

 rapidly effective. It is evident that the amount (depth and frequency) of tillage which would 

 benefit crops on a clay soil might damage those on a sandy one. 



To conserve the water of a loose-textured soil its main tillage should be shallow, so that 

 the bulk of the earth remains compact enough to hold the rain and to transmit bottom-water 

 steadily from the subsoil upwards to the roots of crops. The surface only, which has been 

 puddled by the latter and early rains, need be disturbed in spring-time to prepare a seed-bed 

 and to cover in manure. That surface, as often as it settles to compactness or forms a crust, 

 should be loosened up again with the horse-hoe, so as to maintain over the water-conducting 

 body of compact earth a relatively non-conducting layer of loose soil, to cut off the escape of 

 moisture into the asmosphere. 



Summer tillage, to conserve moisture, should be shallow, and should not extend to the 

 roots, unless, indeed, with the object of compelling them to develop lower down and nearer 

 to the water supply. Generally, however, the depth of the well-manured stratum is but small, 

 and as little as possible of it should be withdrawn by frequent stirring and consequent drying 

 from serving as forage-ground for the roots of crops. 



It is, however, easy to see that the effects of surface tillage will differ according to the 



