TO DISCOVER SOIL DEFECTS 



37 



ditches, on higher lands, has filled the lower level to such an extent 

 that there is actual outcropping of swamps in the swales. The 

 cure for these conditions is, obviously, drainage, which it is not 

 always possible to secure at a warranted outlay. 



Alkali. Connected with this rise of the ground water the alkali 

 evil may intrude. But little trouble arises from this cause in the 

 high-lying, sandy tracts, where irrigation or the natural rainfall 

 carries the soluble salts annually into the country drainage ; but in 

 the low-lying and less pervious soils of swales and valley troughs, 

 which are at the same time intrinsically the richest in available 

 mineral plant food, the accumulation frequently causes consid- 

 erable trouble and difficulty. 



Prospecting for Soil Defects. For subterranean prospecting, 

 Professor Hilgard commends a steel rod not less than a quarter 

 of an inch in diameter (round or square, preferably the latter), well 

 pointed at one end, and provided at the other with a stout iron 

 ring for the reception of a stout cross-handle, such as is used for 

 post-hole augers. With such a prod, or sounding rod, not less than 

 five feet in length, the exploration of the subsoil for hard-pan or 

 dense clay layers becomes a matter of a few minutes. It is easy 

 also to detect thus the presence of underlying layers of quicksand, 

 gravel, or other loose materials through which irrigation water 

 would waste, or which would prevent the rise of bottom water 

 within the reach of plant roots, by the large interspaces between 

 their grains. Any remaining doubts as to the nature of such under- 

 lying materials at particular points can then quickly by solved by 

 the use of a post-hole auger or by digging, for thorough inspection 

 of each foot of depth which may be found desirable. 



