PHYSICAL COMPOSITION OF SOILS. 



103 



MECHANICAL ANALYSIS OF HARDPAN. 



It is doubtful whether this condition of things can be 

 remedied by the usual measure of breaking up the hardpan 

 either by hand or by means of giant-powder blasting. Ex- 

 perience seems to show that the effect is only temporary, and 

 that in the course of time, by the action of the percolating 

 waters, the particles settle back into their original impervious 

 condition. It is just possible, however, that if once penetrated 

 by roots, the intervention of these would permanently destroy 

 the close structure, so as to make this a fair subsoil for the 

 growth of trees and other plants. The writer is not aware that 

 this kind of purely physical hardpan without cement has ever 

 been observed elsewhere. 



This physical condition is doubtless responsible for two other 

 phenomena, viz., the " putty soils," and also certain difficulties 

 experienced in irrigation. 



" Putty Soils " is the name popularly given in the Cotton 

 States, and probably elsewhere, to soils usually occurring in low 

 ground and also known as " cray-fishy." They consist of very 

 uniform, powdery sediment, with little or no coarse sand and 

 still less of clay to render them coherent. When wet these 

 soils behave precisely as would glazier's putty, adhering to the 

 surface of even the best-polished plowshare, so that no furrow- 

 slice can be turned and the plow is soon dragged out of the 

 ground. At a very closely limited condition of moisture such 

 lands may plow fairly well; but when this limit is passed in 

 the least (as sometimes happens in the course of a single day), 

 it turns up only hard clods, which in a few hours of sunshine 

 become so hard that no instrument of tillage short of a sledge- 



