DRAINAGE. 85 



and the opportunity for seasonable harvesting and for fall plowing, 

 all depend more upon the condition of the soil as to moisture than 

 on any other single circumstance. 



For the purpose of illustration, we will suppose an acre of land 

 to be inclosed in a water-tight box, its bottom being four feet 

 below the surface, and its sides reaching to the surface, with no 

 outlet at any point. The whole acre lies open to the rain, and 

 the whole depth is saturated by every heavy storm. This acre of 

 land may have the most thorough cultivation of which it is capa- 

 ble, and may be manured as land was never manured yet, and its 

 produce will inevitably be precarious. In very good seasons it 

 may be fair. In wet seasons it will be weak and badly matured, 

 and in dry ones it will be mean and stunted. It will be the first 

 of May instead of the middle of March when we plow it ; the 

 plowing will paste together more than it crumbles it ; the har- 

 rowing will do as much harm as good ; the seed will probably rot 

 in the ground and have to be planted a second time ; and the 

 growth will be slow except during the short interval (often only 

 a few days) between the conditions of "too wet " and "too dry." 



In short, the soil will be putty one-half of the time, and brick 

 the rest of it : " It girns a' the summer and it greets, a' the winter." 

 It is such a soil as no man can afford to cultivate at all. Now let 

 us knock the bottom out of our box and see the result. Of course 

 we must assume that it is underlaid by a stratum of gravel or other 

 porous material. The water which has filled the spaces between 

 the particles of the soil, lying there until evaporated at the surface, 

 sinks slowly away and leaves the whole mass pervaded by air, the 

 particles themselves holding by absorption enough water to make 

 them sufficiently moist for the highest fertility, but affording very 

 little for the cooling operation of evaporation at the surface. When 

 a heavy rain falls, the soil may be for a short time saturated (soaked 

 full) with water, and this drives out all of the air it has contained. 

 As the water settles away, after the rain, fresh air follows and 

 embraces every atom with its active fertilizing oxygen, and deposits, 

 in the upper layers, carbonic acid, and ammonia, and all else that 

 makes air impure and soil rich. Indeed, the water itself has washed 



