SOILS. 26 



- When the subsoil is loose and leachy, (consisting of an 

 excess of sand or gravel,) thereby allowing the too ready 

 escape of moisture and the soluble portions of manures, the 

 subsoil plow is not only unnecessary, but positively injurious. 

 In this case, the surface soil should be somewhat deepened 

 by the addition of vegetable matters, so as to afford a greater 

 depth through which the soluble manures must settle, be- 

 fore they can get beyond the reach of the roots ; and the 

 supply of moisture would thereby be much augmented. It 

 is better, however, to keep lands of this character in wood or 

 permanent pasture. They are at best, ungrateful soils, and 

 make a poor return for the labor and manure bestowed upon 

 them. 



If there be a diversity in the character of the surface and 

 subsoils, one being inclined to sand and gravel, and the 

 other to marl or clay, a great improyement will be secured, 

 by allowing the plow to reach so far down as to bring up 

 and incorporate with the soil, some of the ingredients in 

 which it is wanting. This admixture is also of remarkable 

 benefit in old or long-cultivated fields, which have become 

 deficient in inorganic matters, and in their texture. 



The effect of long continued cultivation, besides ex- 

 hausting what is essential to the earthy part of plants, is to 

 break down the coarser particles of the soil, by the mechani- 

 cal action of the plow, harrow, &c. ; and in a much more 

 rapid degree, by the chemical combinations, which cultiva- 

 tion and manuring produce. A few years suffice to exhibit 

 striking examples in the formation and decomposition of 

 rocks and stones. Stalactites and various specimens of lime- 

 stone, indurated clays, sandstone and breccias or pudding 

 stones, are formed, in favorable circumstances, almost under 

 our eye; while some limestones, shales, sandstones, &c., 

 break down in large masses annually, from the combined 

 effect of moisture, heat, and frost. The same changes, on a 

 smaller scale, are constantly going forward in the soil, and 

 much more rapidly while under cultivation. The general 

 tendency of these surface changes, is towards pulverisation. 

 The particles forming the soil, from the impalpable mite of 

 dust to the large pebbles, and even the stones and rocks are 

 continually broken up by the combined action of the vital 

 roots, and the manures incorporated with the soil, by which 

 new elements of vegetable food are developed and become 

 available, and in a form so minute as to be imbibed by the 

 epongioles of the roots ; and by the absorbent vessels, they 

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