[409] SCIENTIFIC MANUAL. 123 



stagnates within lass than three feet of the surface, will be 

 materially benefitted by drainage. 



The following extract is from " Barrall on Drainage," 

 under the head of the "External Signs of the Want of 

 Drainage." He says: "The aspect of the soil after 

 heavy rains, or great protracted heat, the mode of culture, 

 and the nature of the vegetation are very conspicuous 

 characteristic signs, by the help of which we can easily tell 

 that a ground needs to be drained. 



" Wherever after a rain, water stays in the furrows ; 

 wherever stiff and plastic earth adheres to the shoes ; 

 wherever the foot of either man or horse makes cavities 

 that retain water, like so many little cisterns ; wherever cat- 

 tle are unable to penetrate without sinking into a kind of 

 mud ; wherever the sun forms on the earth a hard crust, 

 slightly cracked, and compressing the roots of the plants as 

 into a vice ; wherever three or four days after rain, slight 

 depressions in the ground show more moisture than other 

 parts ; wherever a stick, forced into the ground, one foot 

 and a half deep, forms a hole like a little well, having water 

 standing at its bottom ; wherever tradition consecrated, as 

 advantageous, the cultivation of lands by means of convex, 

 high, large ridges ; one may affirm that drainage will pro- 

 duce good effects." 



In addition to the above indications, the growth of 

 certain plants known to thrive only on soils that are wet, 

 or have stagnant water near the surface, will usually 

 indicate to the farmer the soils that need draining. 



It is frequently the case, however, that soils which arc 

 sufficiently drained, when first cleared, to produce healthy 

 aud abundant crops, become wet and sour after some 

 years of cultivation. This has been observed, no doubt, 

 in the experience of many farmers in Georgia. 



Such soils when first cleared are drained by the roots 

 of trees, which gradually decay, leaving ducts through 

 which drainage water passes off to pervious strata below. 



